few questions on injection pumps

[84cucv1ton]

84 m1008 ran. ran pretty good. as time went on lower power. now will not start. at all.. only a few weeks back it ran good. i did all i could think of. could the pump go down hill that fast. truck was sitting for about 2 years

second truck with a new 6.2 4 k on it.. let off the gas to much and it quits. now its getting hard to start. warms up a bit. fires right back up. did what i know. im thinking it the pump on this truck too.. only 4 k and it gone tho

any idea?? could i be missing something ?? thanks for the help

 

[84cucv1ton]

to think of it they are from the 80s. not like they are only a few years old

 

[jward37]

Injection pump can go quickly

Mine went from running great to failed pump in about 15 minutes. There is a disk in the original pumps that just wears out as I understand. Driving from point a to b one day I had to go through 3 gulches here in Hawaii (ravines I think they are called elsewhere), which means I had to pull up an incline 3 times. First gulch, the transmission downshifted to 2nd gear, wierd, 2nd gulch it did it again and barely made it up, 3rd gulch, downshifted to 1st gear and barely made it up. I got to our property, parked it, went through fuel pump replace, filter replace, checked everything. It would start, keep running for a bit if reved, but died if not reved. Replaced pump and it was fine. I had to replace it in an open field in the rain, but you know, the hood kept me dry mostly.

 

[84cucv1ton]

ok sounds like my truck thanks

 

[jward37]

Check other stuff too

I also had other similar problems with a bad fuel pump, which is much easier to replace than the injection pump. You probably know this, but water or air in the fuel filter can cause similar problems and it's easy to bleed both out. Good luck.

 

[84cucv1ton]

bad fuel pump. didnt even come to mind.. how did you check yours? take the hose off and see how it flows? that would be great if it was that

 

[jward37]

Bad fuel pump

It was years ago. I may have checked the pressure coming out of the pump or filter assembly, but cant' remember. Since it was pretty easy to replace, (2 bolts I think), I just got a new one. I also remember I broke the pump drive rod installing the new one, so there was a little trick to putting the new one on. Don't force it as I recall. Somebody else may have more details on how to make sure the rod is properly located when putting on the pump.

 

[jward37]

Fuel pump location

It's on the passenger side, low down near front of engine.

 

[mistaken1]

The -20 manual talks about troubleshooting the fuel pump for flow and pressure. Use a quart container and crank the engine for 15 seconds and measure the volume of fuel in the container. Then put a pressure gauge on the output and see what pressure is (5 to 6 psi ???? check the manual for the exact volume and pressure). Don't for get to remove the pink wire from the IP when testing.

 

[84cucv1ton]

ok thanks

 

[84cucv1ton]

working on this right now... real cold out.. the bottom of the fuel filter is very wet. first step

 

[jward37]

That should be a big clue. Hope your water sensor hasn't gone. That was a difficult part for me to find when mine went. I think you would see the light on on the dash if that happened. This part is what I call made out of unobtainium.

 

[84cucv1ton]

yeah, so far im leaning to a new injection pump. fuel pump is fine..

 

[jward37]

I take the water sensor back. I looked years ago before all these web pages popped up. Looks like you can find the sensor after all. Good luck replacing the injection pump. Lots of fittings.

 

[84cucv1ton]

thanks ill get done

 

[Hasdrubal]

" the bottom of the fuel filter is very wet" Sounds like your filter base is leaking, letting air in and losing prime. Just replaced mine, the usual culprit is the fuel pressure sensor. You can either replace the unit, the new ones delete this sensor, take sensor out and replace o-ring, or block the passage by tapping and threading in a brass plug, someone even filled his with JB weld. Search the site, there are loads of posts about this. New base with filter at ;
Chevrolet Car Parts Surplus $64.99, about halfway down the page.

 

[84cucv1ton]

thanks i found it

 

[jdemaris]

84 m1008 ran. ran pretty good. as time went on lower power. now will not start. at all.. only a few weeks back it ran good. i did all i could think of. could the pump go down hill that fast. truck was sitting for about 2 years

All the pumps built before 1985 had a high-failure plastid ring inside. It was eliminated in all pumps built after, and older pumps when fixed got retrofitted. If a pre-85 pump has been upgraded, it should have a metal tag with and "E" on it.

I've seen pumps blamed for many problems when they weren't. You need to verify you've got air-free fuel getting to it.

The Stanadyne pump requires no fuel pressure, just flow. In fact some are used with no fuel pumps at all.

Usually the first thing to wear on an upgraded pump, is the timing advance. When it stops working, the engine tends to break up at high RPMs.

The "distributor" in the pump will wear out if bad, or low-lube fuel is used a lot. When this happens, often the engine starts well cold, but will not restart when hot.

The DB2 "injection pump" is actually a small dual-piston high pressure pump, hooked to a low pressure rotary vane fuel pump, and a large distributor section on the back - so the one little pump can send fuel to many cylinders.

 

[84cucv1ton]

im getting good fuel to the pump.. fixed the air leaks.. as i turn the key it want to go it seems then it just quits. same think 6 times in a row

 

[jdemaris]

im getting good fuel to the pump.. fixed the air leaks.. as i turn the key it want to go it seems then it just quits. same think 6 times in a row

Still sounds like air to me. Or, too cold, or fuel delivery too low? How cold is it when this is happening? Assuming the temp is over 30F, this is what I'd do.

First thing I'd get a small fuel tank, lay it on the fender or roof, and hook it gravity-feed to the inlet of the filter housing. That will eliminate any possible air intrusion. Then bleed the filter and try it. I've driven a few 6.2s home that way that would not run otherwise. The injection pump cannot work until it is 100% air free.

I've got a rusty diesel 4WD Suburban I bought from a local school. for $250 It would start and die, start and die. Ends up there's a pin-hole somewhere in back, making it suck air. I finally stuck a 5 gallon outboard motor tank in the back seat. Ran a rubber hose all the way to the fuel filter, and then drove it home that way. Runs fine when hooked to that little tank. Note - if you do that, make sure you open the vent on the cap. I forgot at first, and the tank actually started to cave in on itself from the suction from the engine fuel pump.

If still not working, I'd pull the top cover off the pump, look in and verify the linkage is all free and metering valve is not stuck. The metering valve does all the throttle and shut-off work. When turned one way, it shuts the engine off, and then turned all the way the other direction, youi get full throttle.

Not counting all the other controls inside the pump, there isn't much when it comes to just starting the engine. Fuel comes into it, gets controlled by that metering valve I mentioned, then gets sent to two little piston pumps, and then on to the distributor that determines which cylinder gets that little charge of fuel. In most cases, either it works, or it does not - with not much in-between. Note though that if someone messed with the max fuel adjustment, and it is set too low, the engine won't get enough fuel to start when cold.

If that pump sat for many years and got dry, many parts inside could be stuck. Pump pistons, delivery valve, or metering valve.