NEW RESULTS was Chevy Kodiak dumptruck gasoline problems

Ignoramus14054 · 2012-02-29T01:29:17+00:00

Tom, and others, I took some time off this problem, and also took sometime to work on it and diagnose it properly. Yes, this is based on TBI (throttle body injection). We replaced the fuel pump, at least some fuel filters, and injectorbodies. It did not help. Even with new injector bodies, the fuel would, atbest, drip from the injectors. drip, drip, dripThen I decided to NOT take shortcuts and diagnose things properly,using proper troubleshooting techniques, organize my workplace etc. As you know, before the injector bodies, there is a pressureregulator. It has a spring inside. For testing purposes, I removed thespring, essentially disabling pressure regulation.We cranked the engine again, again to the same result. Dripping, notenough fuel. Then I measured the voltage supplied to injector bodies, it sort ofvaried, but would hover around 2 volts. It seemed low. Then, I took out the wires coming from the engine, plugged in mylittle alligator clips, and supplied 4 volts to the injector body,using my DC power supply.Voila, the fuel came out in some force (but not as a shower), theengine would start and run fine.I put the regulator back in and, guess what, no fuel again,even with 4 volts applied to injector bodies. I ended my experiment right there and went home to think.Clearly, without the pressure regulator (at full supplied fuel linepressure), and with more volts supplied to injector bodies, the engineruns. But what des it mean?My current thinking is that I seemingly have two problems1) Lack of fuel pressure 2) Lack of voltage supplied to the TBI. I have a feeling that both items are a manifestation of the sameproblem, which is lack of voltage in the fuel subsystem. I think thatboth the fuel pump is not getting enough volts (so not enough fuelpressure), and also, the injectors are not getting enough volts (sothey do not open properly). Makes sense?If so, what could it be? Bad ground?i

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clare 14 years ago

It will be a very typical regulator - and no spring WILL make no pressure. I've rebuilt and modified those regulators to make them adjustable - friend's 350 TBI engine was running lean due to a combination of lower than spec pressure and a modified Throttle Body. The regulators are, as I said before, notorious for being in-accurate. General spec is between 9 and 13 psi. This one was running at about 8 and dribbled. We set it to 15 and got a real good atomized spray pattern, the fuel consumption dropped, power improved, and the truck didn't run hot any more.

If he followed my instructions in my last post he'll KNOW where the problem is NOT, even if it doesn't pin down exactly what the problem is.

I've worked on this stuff a lot over the years - back when that thing was current, but not so much today.

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clare 14 years ago

Not at all. The ground is in the CONTROL circuit.

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Ignoramus22470 14 years ago

A followup. Very embarrassing and very typical.

What was wrong was that I mixed up the supply and return lines, so the fuel pump was pumping into the return line.

The truck now runs great and I have a foot in my mouth.

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Ed Huntress 14 years ago

Terrific for fuel economy!

That makes it hard to work the clutch and the throttle at the same time.

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dpb 14 years ago

So just out of curiosity what was the original fundamental problem (presuming you didn't receive the truck w/ the lines reversed)?

I'm at least somewhat surprised could do that--on the GM trucks I have here the lines aren't interchangeable--the feed line is larger than return, typically.

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Jim Wilkins 14 years ago

"Ignoramus22470" wrote in message news:NOadnTwtp9PpnMzSnZ2dnUVZ snipped-for-privacy@giganews.com...

Slava Bogy for easy fixes.

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Ignoramus22470 14 years ago

The original problem was bad fuel pump in the tank.

I got the tank separated from the truck and hooked it up wrong. The lines, unfortunately, were interchangeable.

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Bruce L. Bergman (munged human 14 years ago

Oops. There is something to be said for keeping a roll of tape and a Sharpie handy, and tagging things as they come apart so you can make sure they go back together the same way.

And/or take a few pictures before you start, and a few more as you go, of how it went together. (Sometimes you have to make an un-planned stop for a day or two, and totally forget.)

And/or grab a paint marker and permanently mark "Vent" and "Supply" and "Return" on the steel lines once you figure out which is which - then you can check that against the markings on the pump when it's going back together.

I still do silly things that, even when it's a job I've done hundreds of times. 99% of the time it goes back together easy, but there's always the one time in a hundred it doesn't...

Oh, and as you put it back together you put the date on those hoses and clamps and on the fuel pump itself a White Paint Marker is perfect for that. You just replaced the hoses in 2012, no sense in forgetting when you did them last and trying to change them again till at least

2020. Some of those high-pressure fuel hoses are $10 plus a foot.

Date and Mileage on the Oil Filter canister too.

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Ignoramus22470 14 years ago

I received them apart, I never had them assembled correctly.

The tank was on the shelves and the truck was in the yard.

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clare 14 years ago

I hope you at least trimmed your toe-nails first!!!

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clare 14 years ago

So they were reversed AT THE PUMP. I can see that happening if it came to you in pieces and you were not familiar with the system - - - -.

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Ignoramus22470 14 years ago

Exactly. Came in pieces, I was not familiar.

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Bruce L. Bergman (munged human 14 years ago

Oh, missed that part - and it's totally understandable.

That's one of the things that GM usually does, they make the hoses a different size so they can't go together backwards.

Which is maddening because you think you've got a roll of the right hose before you started the job, then you need to stop work and go run off to the Auto Parts and get the other size hose...

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dpb 14 years ago

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Indeed which is why I still find it at least a little puzzling it was doable. But, I've not had a Kodiak version of the Chebby; only the C60 (which is seriously old as in antique) and the C70 is only about 15 yr newer. Since then we've gone to the tractor/trailer route for actual hauling, 4-500 bu that seemed big load way back when just won't cut it now when it's a 2 hr or longer wait-time to unload :( .

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Ignoramus20398 14 years ago

Well, all lines were interchangeable, size wise. Not all could reach to all nipples, but some could (and were) mixed up.

I have decided that until I find a cheap enough and suitable enough semi trailer for my semi tractor, I will use the dump truck and the

15k trailer that I have, for moving industrial surplus stuff around.

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Jon Elson 14 years ago

Oh, GOSH! Well, when working with unfamiliar equipment with multiple hoses, it is easy to have something like this happen. That would certainly foul up the regulator function and explain why the spring worked opposite of how it should. Take the foot out, you DID find and fix the problem, it just took a little bit longer!

Jon

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Jon Elson 14 years ago

Oh MY! Be REALLY careful which handle you grab, or a big lathe could get dumped in the middle of the street!

Jon

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Ignoramus20398 14 years ago

Yes, the excuse I had is that I have never seen it connected correctly, and the lines are compatible even with wrong nipples.

Thanks

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Ignoramus20398 14 years ago

\A scary thought. As a matter of fact, I believe that I cannot operate the dump unless I am in neutral.

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Steve W. 14 years ago

Got your CDL yet? If not I wouldn't be driving that dump around.

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NEW RESULTS was Chevy Kodiak dumptruck gasoline problems

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