new truck barely runs after fuel filter swap

[DLang]

on the way to work friday I filled the tank for the first time since the day I got it (about 370 miles and 22 gallons ago). I then drove to work, but on the way the truck started slowing down. I've had this happen to be before with similar trucks and it's always been the fuel filter. I limped it the last few miles to work and after work changed the fule and air filters (that I had purchased that morning since I knew how bad a clogged fuel filter is).

I drove it home, but it didn't seem to have quite as much power as before, and the couple of blocks were really bad. I then bled all of the injectors (ran the engine, cracked open each injector line, verified that it was squiring fuel and then closed it again). this seemed to help a bit and the truck seemed to be in good shape the rest of the weekend (a couple short trips), but tonight we piled in the truck to go to dinner and about three blocks away from home I found I could barely get up to 25, at four blocks I was barely doing 15. comeing home it would do about 15 on the level, but on a downhill section when the speed got up to about 25 the engine suddenly woke up and it was almost driveable

the fact that it seems to wake up at higher rpm's argues against the fuel filter clogging up again (which was my first thought based on everything else) but I don't know what the right answer is.

I'll probably try bleeding the injector lines again tomorrow to make absolutly sure that I got them all tight again afterwords, but what else should I do?

David Lang

[DmaxMaverick]

Sounds like you got a load of really bad fuel.........Or a tank of gas. What color was the nozzle?

[john8662]

What year model truck are we talking about here?

Please update your "signature" under the "User CP" section in the blue bar above, just put your vehicles information in it to help us better troubleshoot it, there were differences in components from year to year.

J

[DLang]

sorry, it's a 1986 military blazer.

I guess it's remotely possible that I filled it with gas, it would be the first time I've ever made that mistake. I think I've still got the recipt, sot I'll double check.

[DLang]

I double checked that I didn't make a mistake, I did fill with diesel.

I tried bleeding the lines again. while doing so each line that I cracked produced a drop in the idle speed (some more then others)

I changed the fuel filter again.

it still barely wants to idle, let along rev up and give me any power.

any thoguts before I throw up my hands and take it to a dealer?

[john8662]

Take off the fuel return hose on the top of the injection pump and start briefly, make sure you're getting fuel out of the pump.

If the fitting on the top of the injection pump is plugged, it will cause the engine to perform like this and die.

Also, start engine and open the air drain valve on the side of the fuel filter housing and verify that you're getting fuel pressure, this will test the fuel lift pump.

Lastly, this is starting to sound like a bad flex-ring situation in the pump. It's possible you have one in your injection pump being military. To determine this you'll need to remove the top cover of the injection pump and see if there is any floating debris in the fuel inside, if no, then you're probably ok, if yes, it's time for a pump rebuild.

Keep us posted, don't take it to "the dealer" find a repectable diesel shop familiar with the 6.2 as a last ditch effort.

[blockw5chips]

That's what mine started doing. I thought it was fuel filters too. I was about 50 miles(1:30am working) away from home on the interstate when it started loosing power and when I push the pedal more it would just bog down and sputter. I finally made it back to work at 400am. I then drove home and the next day I change filters added some Diesel Kleen and started driving and then out of the blue it started bogging down and would stall if I slowed to make a turn. Then it started pumping out white smoke,I was told it might be sucking air, or it could be the IP(always fix the cheap stuff 1st), then it got put on the back burner(wife's burb burnt fuel pump and wiring). Now I'm back to work on it. The first thing I noticed was my timing marks where way off,3 bolts on IP facing firewall where loose. Realign marks and started it up, ran just fine for about 5+ miles. Started same old stuff, I bought a piece of 1/4 clear tubing and put on the IP fuel return and cranked it up and I could see small bubbles flowing thru, then they started getting bigger and the bigger they got the worse it ran until it finally shut down. When I think back mine slowly got worse over time,I think my mechanical lift pump bit the dust or I have a major air leak somewhere. I gonna install an electric lift pump. I'll let you know what happens pending the T.S. Ernesto. Good Luck:)

[DLang]

Also, start engine and open the air drain valve on the side of the fuel filter housing and verify that you're getting fuel pressure, this will test the fuel lift pump.

I did do this and it does produce a stream of fuel (and it did a good job of re-filling the fuel filter after each change), so I think the lift pump is pumping at least some fuel. the preasure isn't as high as I expected, but it's been several years since I last worked with one of these engines, so my memory is iffy.



Keep us posted, don't take it to "the dealer" find a repectable diesel shop familiar with the 6.2 as a last ditch effort.

I've been hunting for a shop willing to work on diesels (let alone any good at it) in this area (simi valley, california) for several years :( I even had a shop refuse to replace a fan belt becouse it was a diesel.

thanks for the ideas, I'll give the rest of them a try.

David Lang

[DLang]

I disconnected the overflow line from the top of the injector pump and anout 5 seconds after starting the truck it started dumping a little fuel.

I replaces it with a clear tube and started the truck, it filled the tube up to the top of the loop (with a small, but steady flow os tiny bubbles in the fuel, but even when I had someone else rev the engine it never produced much flow through the tube (some, but not much)

how much fuel should I get from there?

David Lang

[john8662]

You should get enough fuel out the line to almost instantly fill the line up with fuel. If you have to wait for the line to fill with fuel, something's not quite right and it could be the fitting in the injection pump is plugged (caution, there is a bead inside, just be aware).

Sounds like the lift pump is working just fine, especially since you mention that you're able to get the filters primed easily. These pumps make around 6-9 psi of fuel pressure at cranking (fully primed system of course).

[DLang]

I pulled that fitting (didn't see the bead, although I was looking for it)

with it removed there was quite a bit more fuel flowing out of the hole, but still not enough to fill the hose 'instantly', I attempted to blow through the fitting and was not able to get a noticable amount of air through it in either direction. when I put the fitting back on and started the engine I had to look closely to see that fuel was comeing out of it the volume was so low.

anyone know the part number to ask for to get a replacement?

[john8662]

I sure don't have a p/n for the fuel return fitting, but any injection pump rebuilder that does stanadyne should be able to get you one. Might check with some of the venders in the advertisers section and see which one of them can find the part for you.

Dig out the phone book and see if there are any injection service places locally, if not I know Diesel Injection Service in my neck of the woods has them www.dieselpage.com.

J

[DLang]

looking at the fitting in daylight I can see through it so it doesn't appear to be blocked (although It does look like there is a little crud in it)

I picked up a replacement lift pump at napa to give that a try (it was only$24 so it's worth the gamble)

David Lang

[DLang]

that fitting on top of the IP turns out to be the problem.

I was checking it again after blowing it out (and realizing that I can see through it, so 'it can't be plugged, can it?') and was lazy so I didn't shut the truck off when I went to remove it. as soon as I turned it a quarter turn the truck's idle speed jumped significantly

I still don't understand why I can see through it, but it's still this much of a problem, but time to try and replace or clean it.

unfortunantly, as far as replacing it goes, it's $46 for the fitting and seal from the dealer, and they would have to order it from flint, MI (I'm in california)

so I'll be trying to figure out a way to clean it.

David Lang

[DmaxMaverick]

The return line may be blocked further downstream. Look for a kinked or bent line. Try blowing air into the return. The air should escape through the fuel filler (be sure to REMOVE the cap).

Even if the line is "open", it may have enough blockage somewhere to cause a rise in return pressure (not enough flow).

[DLang]

after finding that the dealers are estimatig two weeks to get the part I spent some time with a can of brake cleaner and an air compressor.

once I finally got it unstuck the difference in flow through the fitting was drastic. with the engine idleing before I would get just a little flow out of the fitting (it would just run out the fitting and back down the outside) with the fitting clean the jet of fuel rises a good half inch above the fitting before arching back down to land on the engine several inches forward.

I'm about to take the truck out for a road test.

now if this overflow fitting got plugged up from the crud in the fuel that made it as far as the IP, I shudder to think what my injectors must look like. I'll have to look into rebuilding/replacing those. in the meantime it's getting a cleanup dose of injector cleaner additive added to the tank.

[DLang]

the fitting pluged up yet again on my (the last time I soaked it for an hour in brake cleaner before blowing it out and reinstalling it). I called Diesel Injection Service (http://dieselpage.com) to order a replacement. they are telling me that this sounds like the governor ring is falling apart, and the result is that the injector pump needs a complete rebuild :(

does this sound reasonable to you folks?

David Lang

[john8662]

It does sound plausable. The governor or "Flex ring" does fail in the early pumps, and gets updated by an EID assembly that is immune to Diesel fuel (strange huh).

J

[DLang]

when I called to check on IP availability I asked aobut ijectors, I was told that there are two varients of injectors, a fine thread and a corse thread type. is there any way of figuring out what I have other then pulling one out of the truck? (it's hard to drive 120 miles to pick up parts with an injector out :p )

[john8662]

Your '86 will have fine thread long body 6.2 injectors.

The only year 6.2 that had the coarse thread injectors is the '82 models.