Truck won't consistently idle.

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Hello folks, first off, thanks for the information in this conference.

I have a 1992 Ram 250 LE 2wd with 146K miles on it that went from running perfect to instantly missing and not idling while going 4th gear up a pretty good grade. I let water out of the separator, and the sputtering stopped and power pretty much came back, but the idle never did. I replaced the filter/separator, refilling and priming/bleeding as directed. Bled air out of the low pressure bleed using the lift pump, and at the injector fittings while the truck was running.

It idles fine some of the time, then it really dies off, barely runs, oil pressure goes low, etc. (I turn it off so as not to run the engine under this condition). Power is normal - and at times when cold in the mornings, seems much better than normal.

I bled the system several times as mentioned above, and got air all but the last time. One interesting note, the injector closest to the front of the truck, which makes it last in line for fuel, would not bleed air or fuel until the motor was revved. At high idle, no fuel appeared to be there.

Any suggestions to figure this one out? Thanks for any help!
Jon.

 

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almost sound like you mighthave broken a roller or cam plate in the injection pump,
when that happend to me the same problem would come and go, but i was also geting metal shavings stuck in the fuel selinoid and the truck would not shut down sometimes

 

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You might check the fuel lift pump (driver's side of engine, between fuel line from tank and fuel injection pump) for failure. This provides the fuel injection pump with consistant fuel pressure. If it starts to seize up, you will have problems ranging from rough idle to no engine operation. Mine went out recently, causing a rough idle and was replaced by Cummins Southwest for $65 + labor.
Hope this helps,
Steffan Marley

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'93 W250 CC, 4X4, 3. 54 Gearing, NV4500 5sp,
16cm2 Turbo Housing, Pacbrake, Amsoil Bumper
To Bumper W/Bypass, Boost/Pyro/Oil Temp Gauges,
3. 5" Exhaust, HP Injectors, K&N Filter, Hella
Lights, Icom 2 Meter and Uniden CB Radios.

 

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Get this: Read this post Friday, 7-14-2000, thought it sounded like the lift pump was bad on your truck. Mine has been "wet" for a long time and keeps the part of the engine block below it wet also. Anyway, I was in the Colorado/Yuha deserts ( near California/Mexico border) today (7-15-2000) and it was frying pan hot (117F) and I noticed 1) as my truck was facing upgrade I lost 125 rpm at idle and 2) After 10 minutes at idle in a parking lot (NO WAY I was going to shut off the A/C) I saw fuel on the ground directly below the lift pump. This is the first time It has leaked to drop fuel on the ground.

Went by the local parts store this evening and they wanted 119. 99 for a "95% chance "exact" replacement.

I just now called Los Angeles Freightliner in Whittier, CA (open 24 hours, 7 days!!!) they have the Cummins part for $65. 00!

I think I'll drive over tonight.



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'93 W350 Club Cab, 5 sp. , Factory Options: LE, 4. 10, LS, 7600 lb. rear springs, tachometer, front stabilizer bar. Mods: Banks stinger plus, Linex bedliner, 25,000 lb gooseneck, 10,000 lb receiver, Tekonsha brake controller,
PW injectors.

 

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bought one from NAPA last week for about 65 bucks. Still haven't replaced it though.

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1993 Dodge/Cummins D250 LE ext cab 175000 miles

1970 Dodge W300 Powerwagon with 8 ft dump bed

 

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Thanks for the tips! Any suggestions on how to isolate whether the problem is the lift pump or injector pump? The lift pump manual lever does have pressure and does bleed through the low-pressure bleed fitting, and there does not appear to be any fuel leaking aroundit. Anything else to look for to determine if the lift pump is bad, other than swap it out? $65 is probably worth a do-it-yourself swap on that item and the mechanics involved look pretty basic - 146K on the motor so it might be a preventative in the future if it turns out not to be a problem.

Rick, is there anyway to check the injector pump for a broker roller or cam plate? Do I need an inline fuel pressure gauge to figure this one out?

Thanks guys, I appreciate the help!
jon

 

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You can put a T in the fuel line on the output side of the lift pump and check fuel pressure with a gage while driving. It should read 5-7 psi. The symptom of reduced idle speed just because of an attitude change points to the lift pump as it is harder to "suck" the fuel from the tank. The injection pump uses very high pressures that would not be affected by orientation. Even though the manual lever on your pump provides fuel, weakness would show up first under running conditions as the pump is required to work far more.

 

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Picked up the $65 NAPA liftpump today, going to try and find the time to install tonight - looks an awful lot like a normal gas-burner fuel pump.

A little more info. After driving it, the truck idle's fine for up to a minute. Then it degrades quickly to the no-idle state described previously. I have to use some foot on the gas to keep it going. Seems to indicate it has enough fuel to idle for a while, but the liftpump at idle is weak enough that it is not replacing fuel at the rate the injector pump is using it.

What worries me is that twice today, the truck had a hard time shutting off, much like a few replies back described as a symptom of a problem with the injector pump, not the lift pump.

I'll reply with results if that helps folks - thanks for the info.
Jon.

 

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Pump swap went easy. For some reason, the Chilton's manual (still looking for some second hand dodge manuals, hint, hint) said to remove the starter to do this. Probably to get to the pump from below to ensure diesel covers you thoroughly.

I ignored this advice, climbed in head first, and took about 30 minutes to do this, most of the time was spent chiseling off the old gasket.

Bled the low pressure fitting and the manual pump handle - huge difference between old and new just bleeding here. The old one I could barely get to drizzel out of there, the new one almost squirt me in the eye.

Started up, immediately noticed it was smoother through the rpms, and smoother at idle. Test drive showed large power improvements, and much, much smoother. Set the idle, by ear unfortunately, but seemed OK - it is a touch high actually and I'll need to back it off some more.

Lost idle once last night. Drove it for 25 minutes at 75mph down the interstate this morning, and it lost idle again down here at work. The signature is different, and it doesn't loose it completely, but it drops and needs a bit of pedal to get it going again, then it holds it, albeit at the high idle it is set at right now (950rpm or so).
Power is nice, smooth, and as good as it has ever been in the last 4K miles since I bought it.

Could this still be an air problem? I'll re-bleed at the low pressure bleed point, and bleed at the injectors tonight while running to make sure it isn't.

Could this still be a water problem? Someone else mentioned that the tank could need draining to eliminate the possibility (thanks RH!).

Or, am I getting to the point where a cam plate or other issue in the injector pump is the likely cause?

Thanks again for the suggestions and help,
jon.

 

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Hi Jon.

Try completely replacing the fuel filter and filling with clean fuel.

Your tank may indeed need draining. There is a strainer at the fuel pick-up in the tank that may be getting clogged.

Also look carefully at the fuel hose leading to the lift from the tank for any damage that may be letting air in.

Sounds like the lift pump was very weak but not the main source of the problem.



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'93 W350 Club Cab, 5 sp. , Factory Options: LE, 4. 10, LS, 7600 lb. rear springs, tachometer, front stabilizer bar. Mods: Banks stinger plus, Linex bedliner, 25,000 lb gooseneck, 10,000 lb receiver, Tekonsha brake controller,
PW injectors.

 

[Archive]

An update on this, for others that head this direction.

A local mechanic mentioned that I should try to bleed the high pressure fittings off the injector pump itself. Unfortunately, those dudes are way hard to get to all but about 3 of them. I bled the three I could get to, and am going to try a 17mm crow's foot wrench later this week to get to the others.
Anyone recommend a tool to get to these?

I re-bled the low pressure bleed above the injector pump. I re-bled all 6 injectors - boy what a miserable job with the fan blowing diesel all over the place.

I then traced the return lines, from the injectors all the way back to the lift pump and into the injector pump. I used carb cleaner to see if I could find any suction leaks - none appeared visibility, and the motor never seemed to increase rpm's which would indicate carb cleaner was sucked in. I visibly checked the line back to the tank, and could not see any indication of a leak.

The problem seems to not be as chronic as it was prior to all this bleeding and re-bleeding. Power is fine, 20+ mpg on the last tank ending just yesterday, so it was an entire tank of diesel while experiencing this problem.

Next steps, unless others have some suggestions (hint, hint!), are to locate a tool and bleed the rest of the fittings at the pump. Then drain the gas tank and check everything from that end. If these steps don't do it, I'll have to defer to the experts at the local shop and see if they can track it down.

Thought I'd give an update!

Thanks! Jon.

 

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Fixed.

Bleeding the 6 fittings at the fuel pump did it. Found a tool from a friend that would work, a 17mm crow's foot open end wrench with a 1/2 inch socket drive on the power end. Took a grinder to the wrench end to make it low-profile (friend said do it, he no longer has the Mazda it fixed), and got it done.

So, uh, I had to turn up the pump. The smoke limiter (low manifold pressure adjustment) and the full power adjustment. Didn't do the fuel-delivery rate (should I?). It was dark when I test drove it. #ad
This is indescribable. Truck was twice as fast. Completely loosing traction on a dirt road at 50mph in 4th gear and revving into the limiter. Went to the interstate, 5th gear, let her have it over Monument Hill out hear on I-25. Rocket ship over the hill, but the cars behind me disappeared in a plume of so much black smoke that they hit their brakes thinking my truck was coming unglued! Anyhow, the next morning, I had to back off all that power to get to a drivable amount of smoke. Still runs GREAT, but I want the rest of it!

Now, I get smoke at full throttle when the turbo is not spooled up completely, so low revs on the throttle. As soon as the revs come up, smoke goes away.

My questions:
Can I get rid of the smoke and keep the power with adjusting just the two screws I mentioned previously?

Does getting the turbo spinning up help this considerably? So a free-flow exhaust and K&N air filter would be first step, followed by a 14cm turbo housing?

What do the injectors do other than add more fuel? Do they have a better spray pattern so burning is better and more power/less smoke?

Thanks folks! Jon.