The Stovebolt Site Forums The Shop Area Engine Shop 1969 C10 - Engine Blow-By Pressure Vs. Fuel Pump (Pictures posted)

The headers we used on the dyno had thermistors installed to monitor exhaust port temperature. A good-running engine with the right mixture and timing would usually show an exhaust port outlet temperature of 2K degrees F. at full load. Obviously, at lower RPM and load, the temps were considerably less.
Jerry

Jerry you mean thermo-couples, right. Thermistors have limitations well below 2000 deg.

The company that sold me the 8-channel electronic exhaust temp system called 'em "thermistors"- - - -so I didn't try to correct their semantics. They could have called them anything they wanted, as long as I got an accurate, repeatable exhaust port reading.
Jerry

Point taken.

Apache/HotLinc........Looks like the discussion is turning way too high-tech and advanced with all these thermocouples, thermisisters, thermomanns, theoadelites, probably soon getting into tesla coils, deLorean flux capacitors, electrogravetics, Birkeland Currents, and we might end up modifying my ole 69C10 into a red & white flying saucer with a course set for Roswell, New Mexico......and maybe go back in time to the year 1947. Now, if they managed to shoot down my 69 Chevy instead of that freakin alien UFO, then they could have reverse-engineered it, and just imagine how highly advanced our civilization would be by now.

Today I had the amazing insight to go check my 69 Shop Manual, and I went to the Carb section to see if there was another screen after that little "barrel filter" at the entry of the carb. All the drawings show no screens after the barrel filter. I am pretty sure that I saw some type of screen (or maybe just a flat surface with a clogged end). So, Im going to crank the old gal up and get her back in my garage and pull the carb off and investigate. Guess I will also go ahead and attempt a short test drive to see if cleaning that barrell filter helped.

Will update when I know something.
Thanks for all your expert advice.
See your back at Roswell.......maybe I will stash an old weather balloon up under the camper top.

Be sure to bring your foil hat next time......

Joe

......Thats a Big 10-4 from my backdoor,
Or should I say, "Thats a Big Tin Foil from my backdoor.
ha ha.

Update on the 69 C10 issues:

As mentioned before, I cleaned the "barrell gas filter" that fits into the base of the carb. I finally had a chance to give the truck a quick test run, and it "appears" that she is getting plenty of fuel now. I did not want to risk a longer test at the time, so this is just a good sign that the fuel issue is solved......she did not get gas starved and stall out as before. Thanks for pointing me to that barrell fuel filter, as it seems that it was indeed fouled up with enough fine sludge to restrict the gas flow.

Today I pulled the plugs and did a compression test......the plugs are pretty black. I installed the new plugs 3 years ago, and only 650 miles ago. Here are some pics showing the plugs lined up in correct order, and with the compression readings:

Most were consistent and hovering around 140, but No. 8 was a bit low at 122, and 5 was down at 132:

Cylinder: PSI:
1 143
3 135
5 132
7 140
2 142
4 142
6 143
8 122

Is this still in a "good" range, or is that cylinder No. 8 a red flag?

The plugs were black, which I suppose is a sign of running way too rich. I never see any dark smoke coming out of the exhausts, so I dont think it is burning oil. However, a couple plugs do have oil leaking around the plug opening area (will show in next post), and I am guessing that the valve cover gaskets are leaking and oozing down to the plug area.

Next post, with more pics.

Here are some shots showing oil leaking from plugs.

You can see oil coming from the valve covers, but Im not quite sure how it is getting to the plug depressions.

And here are a couple more of the carb base/intake manifold. Does this "sheen" on the intake give evidence that gas is leaking from the carb when running? (I did not notice any drips with it idling).

More pics of those black plugs with only 650 miles on them:
What's your opinion as to whats going on in the cylinders.....just running way too rich, burning a bit of oil (but not enough to show in the exhaust?),

Joe H. wrote a couple pages back:

"Headers pipes thin with age from heat, so your problem could be a combination of low voltage and heat soak. One place to check for voltage drop is the large bulkhead on the firewall with all the wires coming out, the engine harness unhooks from engine side. I have seen more then one have a bad connection."

Joe....Here are a few pics of that firewall connection. Look closely at where the wires go into the connector. Do you think that is plastic "goo" is from overheating wires, or maybe some type of "goo" that the prior owner (30 years ago) put into the connector base to help hold the wires in place? From the pics, what do you think of the condition?

Also, to unplug the connectors and look inside at the prongs/connection points, do you unscrew that bolt in the middle first?

When you look at the pics, there is a "white" wire coming out of the left middle, below the brown wire (with a red crimp connection). It is a kinda of a cloth covered wire with some frays going on......is this that famous "resistor" wire that goes to the ignition? Can a bad "resistor wire" get too warm and cause the "no start when engine warm" condition?

I guess all my posts are not of most interest. Sure would be nice to have more feedback.

I will post another update, although Im not sure if anyone will reply back:

Almost a month since my last post, and I started the truck, and it was again running like crap......sounded like a miss on a couple cylinders, or just running way to rich. Only had it running long enough to pull it forward, and then back up to put in another spot......only had running for about 2-3 minutes. Raised the hood, and found a real bad gas leak around the base of the carb (pictures below). So, I am guessing that the float bowl stop valve is sticking, and letting gas to keep pumping/flowing into the carb and overfilling, leaking out the sides, and also probably leaking down into the intake manifold to the pistons........and maybe the cause of the "no start when hot" issue I have had for the past few years.

So I will order a complete carb rebuild kit and tear into the carb and hopefully find the problem.

So, does anyone agree that this gas pouring into the carb after the engine is turned off has been the root of the "no start when hot" issue that I have had for a few years?

When a thread goes on for a long time without any resolution folks tend to lose interest. Nothing against you or your truck. It’s just human nature. For a ton of information on “Hot starting issues” do a search using the search function in the menu just above your initial post.
As for the Big Bolt in the center of the fuse block.... it is for separating the inside half from the outside half.
I think the goo is a factory sealant.
Rebuild the carburetor and drive it more often. Use real gas if it’s available in your area.
Keep at it, you’ll get it.

Just Horsen Round.......Thanks for some feedback. I thought with alot of pics, that people would be interested and keep sending comments/suggestions........but I understand what you are saying about people losing interest when the thread keeps going on and on and on.

OK.....the goo in the fuse block might be factree sealant.
I just ordered a carb kit, and am hoping that it solves all the issues......including the "no start when hot" issue.

Will do a final repost when I have a final answer after the carb is rebuilt......might help another poor sould down the road.

The reason you're not getting much feedback is that you have a tendency to ignore good advice and make up excuses why things some of us have seen and fixed for probably longer than you've been alive can't be happening. When that happens most of us oldtimers just sit back and watch you struggle. Some folks learn by listening, others learn by watching, and a few people just gotta pee on the electric fence and learn the hard way.

Those plugs are fuel fouled. The rough running and fuel stains on the intake manifold confirm it. Yes, you need a good carburetor rebuild, and that needs to include a long soak of all the metal pieces in a strong dip cleaner, followed by a thorough HOT water rinse and a ridiculous volume of air blown through all the passages with a high pressure air nozzle with a needle-point tip on it. Soaking and rinsing softens the crud, then the air blows it away. There are no shortcuts to getting a carburetor clean, and the stuff in the spray cans isn't sufficient to do that. Follow the instructions in the rebuild kit to the letter- - - - -they're not suggestions. The Rochester 2 barrel has a power valve- - - - -it's under the long spring-loaded plunger that's in the top assembly. Be very sure the power valve plunger works freely and the check valve it moves is completely free of gunk and varnish. When manifold vacuum is low, the plunger forces the valve open and gasoline bypasses the main jets. A stuck plunger or power valve guarantees a too-rich mixture all the time.

Have you made and installed a starter heat shield yet?
Jerry

On the firewall harness connection, you need to pull the bolt out and separate the harness from the firewall. If the power feed wire has been hot, you be able to see it. The goo is a sealant made from some sort of tar based material. It's been a while and I don't really remember all the details of your problems, but a carb rebuild is next on your list. Get it really clean, find a soak tank if all possible, if not use plenty of carb cleaner in all the passages. Once you get it rebuilt, replace the spark plugs and 90% of your problems will go away.

While you have the carb apart, give the float a good shake to make sure that it doesn't have a leak for gas to get in. This will prevent the float valve from closing and cause the gas to leak just as yours is doing.
I have had an incredible rash of leaky brass floats on just about everything that I have been working on lately.
THREE brand new fuel sending unit floats, and a carburetor float in a Tecumseh minibike engine.
I am beginning to wonder if there is something in today's fuel which is eating solder.

Hotrod Lincoln: In reply to your last post:

Perhaps its just the way that emails can be read and interpreted, but yours do come accross at times with a harsh tone and a bit accusatory.

I note that there are many people who come rushing to this site with an emergency mechanical problem, screaming for help, and usually a few of you long-term guys will try to help. Then that poster just disappears without posting pictures of the issue, and never follows-up with a status report. Those guys are the ones you should be leaving negative comments at their posts, and maybe others would learn to have more manners at this site.

If you notice, I try my best to take the extra time to shoot pictures and download them into my posts, and I try to be as descriptive as I can regarding the issues. I hope that my posts and detailed pictures will help others in the future who come to this site looking for answers. At least I am not that guy who is squeezing you for your expert help, and then disappearing without even a "thank you" and a follow up to his posts.

I do admit that it takes me alot longer to get these bizarre mechanical issues resolved, but each of us have life issues which are not readily apparent in these discussions. For example, my 99 year old dad had a stroke a few years ago and now lives in my home.....yep, I am his sole care-giver. So, my wrench-turning time is limited. You comment as if I am a young punk, but I will bet that you and I are roughly the same age......maybe we both should stand near that electric fence and see who can pee the furthest.

You are completely wrong in saying that "I ignore good advice". If you follow all the old posts, you will see that I often replaced parts that were suggested by the experts here. However, I listen and digest all the advice, and just do not rush out and do repair work or buy parts that might not be needed. Only a fool would do that, the same fools that like to pee on electric fences.

In the case of the "No start when Hot" issue, I have replaced the battery cables, battery, starter, solenoid, plugs, wires, voltage regulator, points, plugs, rotor, distrib. cap, fuel pump, fuel filters, and have still had the "no start when hot" issue......and other issues developed. So, now I think I am near the end of this crazy ride and think the carb rebuild will solve the problem.

The truck has run fine for 30 years of my ownership without a heat shield on the starter. If the carb rebuild does not solve the issue, then the heat shield will be the next thing I should try.

Thanks for the carb rebuild tips. Maybe I will hang the carb on that electric fence and try peeing on it.....wonder if I should take a pic for the next post. Ha ha.

Joe H......I agree.....the carb rebuild is next........and I hope 100% of the problems go away.

52 Carl......Good point about those brass floats leaking. A few weeks ago I pulled out the sending unit inside the gas tank on the 69 C10, and that brass float also had a small leak in it.....put a new one on, and now I have a working fuel gauge. Will tear into the carb, and let you know what I find. Funny.....maybe the ethanol is in fact eating solder.

My bet is on HRL. (Think SW Tennessee race horse.)

Dwight, back a number of posts you posted photos of the plugs - those plugs are carbon-fouled from the engine running too rich, as others have said. Carb rebuild and adjustment should handle that.

But with regard to the no-start when hot issue, I'm thinking bad coil at this point. I skimmed the 7 pages of posts, and I didn't see that had been replaced. Maybe I missed it. Before throwing another part at the truck, you may be able to diagnose by warming the coil with a heat gun, or alternatively cooling it when in the no-start condition with electronics diagnostic cold-spray. In a pinch, dust-off spray can work, so long as you get a good blast of liquid, not just gas. Or even easier, if you have a known-good coil, do a quick swap when in no-start condition.

52 Carl.......That would be one heck of a "[censored] contest" for sure.

DrDoug......Yep, those plugs did have signs of having too much gas sloshed in on them......bet the poor things could barely manage a spark being so wet. Good idea about the coil......I will have to check my records again, as I am not sure if that was replaced over this "no start when hot" period ( 2-3 years). Will do the carb rebuild first, and see if that makes most of the gremlins run away.

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Greetings again....It has been almost a year since my last post here regarding "No start when engine is Warm". I did confirm that gas was leaking past the carb and down into the intake. It would start fine, but then begin to flood out due to way too much gas being pumped down into the intake.

So I removed the carb and replaced the old float and needle valve with a new one. Took truck for a drive, and it still was leaking gas around the outside of the carb. So, I bought a remanufactured carb from Rock Auto and thought that this would surely solve the problem. I installed the new carb, and took the truck for a good test drive. She ran great.....very smooth, plenty of power.....no issues. This time there was no sign of any gas leaking around the carb. I then took the truck for a 20 minute drive, turned the engine off, and tried to re-start. This time, the same problem occurred......the engine would barely turn over, and would not start. Almost as if the battery was almost dead. However, I checked the battery, and it was reading 12.85 volts, and the battery is almost new.

I am completely baffled as to what this 5 year old problem is. I have replaced almost everything.....starter, fuel pump, battery cables, battery, cleaned all grounds, plugs/wires/points/condensor, carb. I believe the only item not replaced is the alternator......is it possible that when the alternator is warm, that it will actually draw a full load from the battery when trying to start the engine????? (However, I recall another time last year when the truck failed to start when warm, and I got a jump-start from a new large truck, and the engine would barely turn over, but did manage to start). So I doubt that I have alternator issues.

Any suggestions as to what the problem could be?

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I'm real curious about the problem and the solution.

Volts don't start an engine. Amps do. Try another new battery even though you've have a "new" one in there?

I'll admit I haven't reread the whole thread.

Good luck!!

Wally...........Yep, sooner or later I will discover the problem and will let everyone know. But in the meantime, any and all suggestions are appreciated.
Heck, maybe its that darn Koronna Bug that infected my poor ole 69 Chevy.

Cable ends need to be cleaned. That is where you need to start regardless if you just got done doing that 10 minutes ago.
You have thrown every part at it which I can think of. Now its time to get back to basics. Start with removing and cleaning the cable ends. I hope that you do not have those replacement battery cable connectors which hold the wire on to them with two bolts and a bent piece of metal.

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52Carl......Oakie Doakie......I will check those cables again. You can see in the bottom of this pic that the cables are solid/sealed ends. Only issue is the negative battery disconnect switch, which was added after the "no start when hot" issue started.

But I do need to start at the basics and again try to narrow this down.

I hope that you did not take my post as some kind of lecture. It would be better described as me sharing a conversation I often have with myself whenever I get carried away and get ahead of myself, while neglecting to start with the basics.
I talk to myself a lot, but I don't always listen.

52 Carl........Nope, by no means.....I appreciate all feedback, as thats the only way I will finally "figger" this wierd thing out. We might all sit back and laugh when I finally discover the gremlin that has been haunting my ole truck. If not, are you in the market for one fine 69 C10.....ha ha.

I use to have a '69 C10 Custom with factory air. I wish I still had it.

52Carl: And maybe you could have this blue Bowtie sitting your garage, bringing back those great memories........how about cleaning the summer bugs out of the chrome and blue bowtie on the hood?

[img]https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/download/Number/17773/filename/STA76996.JPG[/img]

And hours of staring down at that fine Chevy dash: I bought this truck with around 102k original miles, and 30 years later she is sporting only about 123k.


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Even has about a full tank so you can drive her home (but dont turn her off until you get home....ha ha):

[img]https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/download/Number/17774/filename/STA76925.JPG[/img]

Unlike your 69, mine came with the optional factree air with the controls on the door......roll down the winders and cigar vent.

In the "What did you get done on your Stovebolt" thread, GIJOE298 said:

"replaced the starter solenoid today. would start fine cold but starter would really drag when engine was hot. seemed to fix the problem."

Don't know what engine he has.

Wally.....Thanks for that info. This "warm/no start" issue started back when the old starter/solenoid was on the truck. The starter/solenoid was replaced with new ones, and I still had the "warm/no start" problem. Also, the autoparts place tested the old starter and said it was still good.

As soon as I have time, Im gonna make a heat shield for the starter and see if that helps any. As someone said, as the headers get old (now 30 yrs old), they get thinner, and could be radiating more heat toward the starter/solenoid, which is only a couple inches away from the pipes.

Update on 1969 C10 "No start when Hot" issue:

Today I fabricated a heat shield to put between the header pipes and the starter/solenoid as was suggested by a forum member. It was 75 degrees here today, and she started up fine and drove great. Drove for 15 minutes and came back and turned off the engine. I then tried to start, and the same issue happened......the engine would barely turn over, and would not start. I raised the hood, and had to wait about 10 minutes, and then she started right up.

While driving, the water temp gauge was normal, and slightly on the "cool" side.....operating in the range she has been at for 30 years.
However, for the first 5 minutes, the Oil Pressure was very high.....almost touching the "H" letter on the factory gauge. To my knowledge, it has never been this high before. After warming up longer, and driving on the highway 55-60 mph, the Oil Pressure was reading on the 3/4 mark of the gauge. When dipping the clutch, popping her into neutral, and allowing the engine to idle, the Oil Pressure would then drop down to about the 1/4 mark on the gauge.

Is this High Oil Pressure a sign of something going on inside the engine, which could contribute to the "no start when engine is fully warmed-up"?
Maybe I need to drop the oil pan and check the pick-up screen on the oil pump?
Other ideas?

Pic of the Oil Pressure Gauge....

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Hi Dwight

I have quickly read most of this thread, and if it has already been mentioned/diagnosed please disregard. I have had similar experiences with heavy trucks (Class 8) not cranking well when hot, and diagnosing them can be a bit tricky. A couple things that I would check:

1- Voltage drop on starting circuit - do a control test on both + and - circuits when engine is cold, and then the same when the engine is hot. Even though the cables are new and sealed, I have seen dozens of cables in my career that have been green and rotted 6 inches back from the terminal, and if that is the case, heat may expand the damaged area and limit the contact within the wire.

2- Amp Draw on starter - Again do a control test (cold) and compare to a hot engine test, if your amp draw is significantly higher I would be looking at internal starter issue's.

Like the others have said, back to the basics, and just because its a new part doesn't always mean its a good part!

I'm sure everyone involved would like to see the outcome, so please let us know how you do.

PS: the picture you posted is very focused on the fuel gauge, Where you just showing what the oil pressure gauge looks like, or trying to show how high it is reading?

Good Luck
Jeremy

Jeremy......thanks for your comments and suggestions. I will give your tips a try after doing the following:

Carl52 suggested that I put a torque wrench on the harmonic balancer and give her a turn when the engine is cold, and then compare the amount of torque needed when it is hot. If the engine cranks real hard with the torque wrench when hot, then the problem is something internal. Im hoping this test shows about the same torque on the wrench on the cold and hot engines.

My other thought would be the water pump.....maybe that sucker is getting hot and causing a drag.

So, I will keep prodding and testing, and will post what I find.

Oil Pressure Gauge.....that was just a picture I had to show the gauge (engine was off). I will try to take a pic of the High Oil Pressure reading the next time I take her on a test run.


Thanks.

No Start When Hot issue.........latest and not-so-greatest:

OK......A few days ago I used a torque wrench to try to measure the resistance as I turned the COLD engine by hand. Did not have a bolt on the front of the harmonic balancer pulley, so I used the torque wrench on the large bolt on the alternator pulley. I had to hold the belt together to make it tighter as I torqued the wrench, and it did not take alot of effort to rotate. I could also rotate the fan blades by hand, also holding the belt a bit tighter. I then took the truck for a 15 minute drive, got all the juices warmed up. Came back, and once again the starter did not want to turn the engine over....just a feeble attempt, turning the crank some with much effort. I then tried to turn the fan blade by hand, but could not. I used the Torque wrench on the alt. pulley, and had to dial up the wrench a couple revolutions before it would turn w/o "clicking" from the wrench.

So, there is something "apparently" internal that causes resistance when warmed up........and ideas?

More gremlins: I had also measured the battery voltage when getting back from that test drive. Had the motor running at idle, and saw that the battery voltage was climbing up toward 18 volts! Way too much. So I thought that maybe the battery was boiling while driving, and screwing up the amperage output of battery when trying to re-start. So, I figured that maybe the voltage regulator was the problem with this "No start when Hot" issue. I put a new Voltage Regulator on, and she was now charging properly in the 14 volt range, and cutting off as it should. Took her for another test drive, came back, and tried to re-start.......once again, same issue, the engine barely turned over. Battery was reading about 13.5 volts after turning off engine, and before trying to crank.

I had also heard a short squealing noise as I pushed the carb. linkage back n forth to gun the engine rpms.......at first I thought it was a bad bearing someplace, or squealing waterpump. Used a long screwdriver to check for noises around the engine.....waterpump was making a normal sound of water rushing thru, no squealing. Front main bearing at oil pan front was fine. Alternator sounded fine, and I detected nothing else around the engine block as the engine was revved up/down. Turned out it was just a loose belt going to the alternator.....tightened that, and those squeals went away.

Engine cranks fine, idles great, revs up/down and drives down the highway fine........so, what internal issues could be going on? Regarding High Oil Pressure: she does start up and read close to the "H" mark, but within a few minutes is down to the 3/4 mark......and at idle she goes down to 1/4........so, Im guessing that the Oil Pressure, although high when cold, is not signalling a problem.

Thanks for more ideas.


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The next time you drive it and it refuses to turn over with the starter, remove the fan belt to see if either the water pump or the alternator is bound up.

52Carl........10-4 on the belt removal.

I also went ahead and installed new super quality battery cables today.....just to cross out the slight chance of something bad internally on the cables.

Will 'spearmint some more and let you know what develops.