Engine/Transmission (1994 - 1998) Power Loss and Engine Quit

[HomerDog]

Hello,

1996 3500 just hitting 200K and engine has always ran great. Yesterday with no indications at an easy 40 mph I lost power and the engine died. I made sure I wasn't out of fuel (gas gauge doesn't work) and later confirmed I had at least 1/2 of tank. Pumped primer button several times and the truck started very rough but eventually smoothed out and ran normal. Made it about 5 minutes down the road and same thing happened. This time it never started again and I had it towed home. As I pumped the primer button hand was getting wet from fuel. Does this sound like a bad lift pump? Any inputs appreciated, thanks.

 

[GAmes]

You certainly shouldn't be getting wet from fuel. However, the primer button isn't the part of the pump that supplies fuel to the engine when the engine is running. Verify that the fuel shut off solenoid is lifting to the full up position, and that it stays up after the engine has started. I have never had a lift pump fail but I suppose it is possible. In my case the pumps started clicking and gave me plenty of warning that the return spring was failing. Perhaps this will help. Joe G's fuel system writeup - Dodge Cummins Diesel Forum

 

[HomerDog]

GAmes, thanks for your reply. Shutoff solenoid is fairly new and I checked it for proper operation. I put in a spare overflow valve just to eliminate that. I know that lift pump failure is rare on these 12v that is why I am stuck as to where to go. I R/Rd fuel filter to get some room for inspection and didn't see anything obvious. Even if some of the fuel supply or return lines were bad would that cause sudden engine stall? That is where I am stuck as the engine ran great at the time. I suspected the lift pump was shot due to fuel on my hand as I pumped the primer. Thanks for any input

 

[GAmes]

I'm sure that Joe G's article can help. If you look at the cutaway diagram you willl see that the pump is composed of two pumps. One is the hand primer, the other powered by the engine. Internals do break, so it is possible that the pump has failed. A fuel pressure gauge would verify it. Bad fuel lines usually manifest themselves as a hard to start engine, but any air leak can cause it. Have you removed the fuel heater puck? If the pump is the original you have 200k miles of use, so replacing it isn't a bad idea, but I hate throwing parts at a problem.

 

[HomerDog]

Thanks again, I have read Joe G's article many times and I understand the fuel system. A pressure gage would be great but I can't get it started. I replaced fuel heater/filter a few years back but the next time I take it off I will leave it off. I agree lift pump should be replaced after 200K but am still stuck on what caused engine to stall with no warning and then start back up to die 5 minutes later. Thanks, I appreciate any opinions.

 

[Missouri Mule]

HomerDog, lift (transfer) pump has 3 check valves in it one or more could have went bad.

It seems that I read a thread or two that a member stated that there is an o-ring on the primer button rod at the pump. It doesn't show one the diagram in the Factory service manual. ( I accidently pulled the cover off the primer button once. It went back on rather easy I just screwed it back on clock wise).



There also is the possiblity that the p7100 bit the dust.



Have you tried bleeding the fuel filter when primming ?

 

[HomerDog]

Bill,

Thank you for the reply. I did bleed the fuel filter when priming and I opened 2 injector lines. The rubber cover on the priming button is shot and I'm getting fuel on my hand when pumping. I'm hoping to not replace the lift pump until I know what the problem is. Please don't let it be the P7100 going south. Thank you for your input, I've read your posts for 10+ years.

 

[HomerDog]

Update-I went back this a. m. for a closer inspection. The primer button boot was torn so I took it off and started pumping. As I pump fuel is coming right out of the button. According to Joe G's fuel write up the button can be removed and o-ring replaced with the pump on the engine. Does anyone know how this comes off and can I buy a new lift pump and take the primer button off it? I figured I'd give it a try if the pump still works but is just leaking so I can get it started.

 

[GAmes]

I have an old pump in the garage. Look where the boot snaps on. The fitting has 2 flat sides. I removed it with a pr of channel locks. There is a plunger and spring. The seal is fastened to the wall of the pmp, not to the plunger. I tried removing it, no dice without tearing it up. Then, to reinstall the fitting (plastic) was a challenge. That is on a work bench, it would really be difficult while bent over the fender. If you buy a new lift pump just install it. I certainly wouldn't take parts out of a new pump to install in an old pump. Besides, I don't think that will fix the original problem. I could be wrong, but I think a new lift pump will fix it.

 

[Nyoest]

You need to get a pressure reading on your lift pump before you spend any money. For temporary use a grease gun hose and el cheapo oil pressure gauge will do.

I can't explain it but when my truck was down for a while I primed the fuel system and fuel was leaking all around the primer knob. It was 1 am so I just started the truck. It quit leaking and haven't had a problem with it 15k miles with 3 filter changes. Dang ol Murphy.

 

[Missouri Mule]

I'm with GAmes if your going to buy a new lift pump put it on don't replace parts.

Since the FSM is about replacing parts and not repairing them I have no idea how the primer button/rod would come off but do search for "Joe G. " and pm or e-mail him (Haven't seen him on this site for a while). Should be albe to get O-ring from auto parts store.



I still have my original lift pump with 259,000 on it still going strong. If it turns out to be the lift pump you can get it from Geno's. It is the piston type ( in the catalog they have them description in the wrong places, page 19 on the bottom).

But make sure you have don't have fuel comming out of it. When you prime and crack the supply banjo to the filter you should get diesel out of it(once you replace the o-ring). But you can try cranking it to see if you are getting fuel there.

 

[HomerDog]

Thanks for the replies. GAmes, I appreciate you testing out your old pump. Based on what you said I'm not going to mess with trying to fix my primer button--I think I will put in a new lift pump, change the fuel hoses while I'm in there and see where it takes me. I've checked the fuel shutoff solenoid again and it's working as advertised. I'll post back when I get the pump changed. Thanks again gentlemen,

 

[HomerDog]

Update. Replaced lift pump and added fuel pressure gage at the filter housing, started engine and had low fuel pressure around 12 psi. Noticed fuel leaking from the top of new filter I just installed. Took filter off and discovered that the shaft the filter screws on was loose. Tightened it back up back up and put on new filter. Started up fine and the fuel\water separator drain is now leaking, still around 12 psi. Installed new WIF sensor and a new OFV and I have no leaks and about 32 psi at idle. I haven't driven the truck yet but hope it's fixed. My conclusions are that the lift pump was shot, at least the leaking primer button portion. As the fuel filter came loose it sucked in air and caused the engine to quit. I try to prime engine but can't due bad lift pump primer and/or just pushing air into the P7100. Any thoughts?

 

[GAmes]

Sounds like you fixed it. I couldn't wait as long as you did, but persistance will pay off.

 

[Missouri Mule]

HomerDog, crack open banjo bolt on supply line to filter, then push primer button until you see fuel coming out with no bubbles. OFV should squeak when p7100 is getting fuel after you tighten banjo bolt and push primer at least 30 times.

You mite have to crack an injector line open at injector and crank enigne a few times but crack ing the supply line should work.

 

[HomerDog]

GAmes, Bill thanks for your input the truck is fixed. It was that loose shaft that the fuel filter screws on was causing the filter to loosen up. Lift pump also needed replacing as it was leaking. When I shook the removed pump I could hear rattling so I removed the plastic portion of the primer button--A one inch socket easily removed it. A small piece of metal came out so something was broke. Truck also idles better with new pump. Best tips I learned from this board was to use a jack to help remove the top starter bolt (I used a small bottle jack and a piece of wood) and use the studs on the lift pump. Thanks again.