96 12v cummins wont stay running...
 

Hello, let me start off by saying Ive owned this truck (1996 2500 12 valve cummins) for two months and I have never owned a diesel before. One day I went to leave work and with no prior signs my truck started up ran rough for a min or so then died. I changed my fuel filter and did not fill it with fuel first and used the primer button but nothing would pump into the filter. Finally I bought fuel and topped off the filter and reattached it, still wouldn't start. Had it towed home. Now at home Ive been fooling around with it and so far I have dropped the pre-filter and cleaned it out and put new fuel in it, put 4 gallons in my tank and removed the fuel filter and pumped the primer and now fuel comes out. So I put the filter back on and didn't tighten it all the way down and primed it until fuel spilled over then I tightened it back down primed the lift pump more and it fired up! However it only will run for a few mins then dies, I have repeated the process of cracking the fuel filter and letting air hiss out and re-priming and tightening it back down and then priming some more and it will fire up again, I have done this now 4 times and my little thumbs are killing me from priming so much. Any ideas of what could be going on?!?!?! Please any advice is helpful and thanks in advance. :argh:

Sounds like the diaphragm in your lift pump has had it. How many miles are on it?

Yeah low fuel pressure delivery, low volume ... does your oil smell like diesel ?? :humm:

Someone did mention that the diaphragm might be shot in the lift pump, haven't smelled my oil but i will check it out, also has 387xxx miles lol. One other thing I forgot to mention is while priming it a little bit of fuel leaks out around the primer button.

New lift pump and gaskets are $100. If there's any chance at all it's original, just do it.

I ordered a new lift pump and will start there. Any other advice out the, how hard is it to change that lift pump?

Depends on you're experience. Honestly, it's a royal PITA, but you can do it with basic hand tools and some patience. Obviously a lift makes it about 1,000x easier, but it isn't necessary, and it's still a PITA. My advice, (if it's 4WD) disconnect the front drive shaft from the pumpkin and swing it out of the way. Take out the starter. You can do it all from the bottom, but when you're trying to get all the holes lined up to install the new one between the bolts, pump flange, heater plate and two gaskets, you'll probably want more than one angle of attack to keep the stress down. In which case, you may want to remove the fuel filter too.

Does it matter if my pre heater electrical lines have corroded away from the heater part on the top of the pre filter? That's another thing I discovered while pulling and cleaning the pre filter. A diesel mechanic i know seems to think it will run fine without the wire harness hooked up to the pre filter.

It will, although it's good to have in the winter, especially up north. I can pretty much guarantee that isn't your problem though.

the wires can be fixed later .. or just Delete the Fuel Heater all together ..

I wouldn't delete it, not in Michigan...

Just a update, I pulled the lift pump in less than 20 mins. I just pulled the tire off and pulled the wheel well cover out and accessed it through there. needless to say I won't have the new lift pump until Monday. Not even sure it wasn't the lift pump in the first place because the gasket is totally gone. I suspect it was leaking through where the gasket was supposed to be. On a side note is the fuel heater part of the system where you plug the tuck in to your houses electrical to keep it warm in the winter?

No that is a block heater, the fuel heater is the plastic portion to the left of your fuel pump. It is sandwiched in between two metal sections and had a two wire connection coming out of it. They are well known for being a source of air leaking into the fuel system on these trucks.

How do you delete the fuel heater

pull the fuel bowl off the Lift pump, remove the hex bolt from heater section and screw the fuel bowl back on ... unplug the heater section from the wiring @ connector... Deleted complete.. :tu:

Update: I received the new pump today...it is about a hundred times more difficult to install this than to remove it. I finally got it all mounted and installed, up until reconnecting the rubber house from the fuel heater/pre filter...it kinks now and I cut a little of the line off and it still kinks and won't fit on all the way now...what seemed like the easiest thing to do is now holding me up from completing the job. I hope when this is all said and done that this is the problem in the first place!:scare2:

Replace it with BIO_fuel grade line .. Gates makes Bio-Guard .. 2.39 a foot @ car Quest

Ok, I went to carquest this morning and had them cut me a foot of new hose. When I cut it to length and put it on, it still kinks...My question is what purpose does that hose serve? Is that the hose that fuel is sucked through when I am pushing the primer button, does it all start at the pre filter then is pulled through that hose and into my lift pump then pumped up to my fuel filter? Also would it be ok if I used more than a foot possibly two feet and loop it around to prevent it from kinking? Kind of making a long loop to drop down a little and connect the pre filter to the lift pump is what I plan on doing.:argh:

Ok i got a longer hose and she's all hooked up now, but I've been priming and priming but nothing is coming up to the fuel filter. I've pressed the primer over a hundred times and i tried cranking it over but no luck, i even cracked the fuel filter and a fuel line still nothing....HELP!

Well that's odd.

Actually, if you're being literal it isn't. When I change my filter I count pumps. Don't know why. OCD tendencies? Eccentric stupidity? Don't know. Moral is: 100 pumps is never enough, and I don't completely drain the canister. I'm usually closer to 200 before I get fuel out the top (I have a little ball valve on the return line on the filter housing I open to know when it's full). Regardless, I'd say crack the feed line on the LP and see if it's pulling anything. I find it very hard to believe in the possibility of a bad LP right out of the box, but it's a pretty simple system and there's only so many parts between the tank and the filter.

I'll keep at it... I just read a big artical on the fuel system apparently the sensor electrical wires that hook up to the fuel heater can leak air thru the plug part on the fuel heater, if you can even understand what I'm describing haha. Which my electrical lines were corroded and crumbled off my fuel heater...not sure if that could be a problem, it's all very frustrating, should I keep the fuel filter cracked open, that seemed to help when the old lift pump was on it allowed me to know when it was topped off.

I give up I've pressed that primer bulb a thousand Times and nothing is coming out...not sure what else to do now besides calling a shop and paying someone

You will need to delete the fuel heater, I think thats why its not pumping up ... its pulling vaccum and not fuel ... hence its not priming ..:humm:

I guess it's worth a shot, seems odd that my "old" lp was pulling fuel to the filter but the truck wouldn't stay running for more than a few mins with out having to re-prime. I just feel defeated.

I Completley Understand that feeling ... 5k truck and I have "Invested" yet again about 35oo since my purchace about a year ago ... :ouch: