Fuel system driving me nuts among other things

[Headshot zod]

Anyway..... Here's the deal, somewhere I have a possible air leak in the system. This has been going on for a year and half now. I need to park the truck nose down and it starts fine everytime. I have changed the mechnical fuel pump and the solenoid.



It is also possible that if there is anything 100% rubber in the inj. pump that it may have dissolved a bit due to almost 4 straight months of B100 use 2 years ago. Sometimes with the lever on the mechanical pump I cannot get a prime going. So I am not really thinking its the inj. pump, but more probably air. It there anyway to pump w/an electric fuel pump and bypass the mechanical system entirely. I saw a post recently that somebody was doing it and I can't remember where I saw it here it wasn't a FASS but a Big Dog something or other.



I don't want to replace the Inj Pump as I have almost all the parts for a p-pump conversion but no cash to finish it since I had so many months of unemployment earlier this year.

 

[Headshot zod]

I found this little tidbit on a marine site.



On all engines using mechanical fuel pumps, including diesels, the existing pump will be unhindered even if the electric fuel pump is deactivated. This means that if the electric pump is turned off, the existing pump will pull fuel through the electric pump without any restriction. Therefore, you can use the electric pump only for priming or as a backup-pump if the existing pump ever fails. Running the electric pump at all times will not cause any problems, but may not be necessary in some cases. On outboard motors that use a suction diaphragm pump, it may not be possible for it to pull fuel through the electric pump. So in this case, use the electric pump as the primary pump wiring it to the boat's ignition switch at the ignition terminal. An on/off toggle switch is unnecessary.



So could I use a push style pump between the tank and the mechanical pump to make sure there is pressure in the system before starting?

 

[cerberusiam]

The lever not working on the lift pump is normal. Sometimes the cam will stop with internal lever depressed and you cannot use the lever to prime.



Air leaks are common in both the metal and rubber lines between the tank and the LP. A small crack won't leak fuelbut it will ingest air and cause hard starts.



You might want to pull the fuel pickup assembly out of the tank and makke sure there is no FOD floating around in there or stuck to the pickup. You could have something loose on the unit or a small piece of plastic floating around the pickup.

 

[JLEONARD]

If you decide to incorporate an electric pump, I recommend a Walbro model 6802. I put one in my current boat to use for priming duties when necessary, and to be available as a back up. 7 psi and 43 gal/hr capacity, continuous duty, 18,000 hour life

I got it thru www.autoperformanceengineering.com

 

[Headshot zod]

Thanks all... I tried ordering a few hours after your post and it didn't work but the order is now processed.



anybody here who has ever perused any of the diesel boating forums will notice that Jlo posts there even more then he posts here.



Busy guy... . Thanks.....

 

[Headshot zod]

The 6802 has arrived, I hope to get it in this weekend

 

[Jgolden]

My motorhome came with that Walbro pump installed, and I recently replaced it(15 yrs old). Without it I could still run but in fuel gulping situations I could tell it (the old one) wasn't working. Well; after the fact I realized it. (Oh so thats why... ... )

In my previous RV, a gasser the GM 454 would not run above idle with out the electric booster. There was also a story of the elec. pump filling the crankcase with gas when the diaphram on the stock engine pump broke. Hard to believe, but possible I guess.

The pump on the gasser was wired through an oil pressure cut off . Newer(90's by my definition) ones use a Ford style impact switch. Never did like riding around with 90 gal of gasoline right below me.

 

[Headshot zod]

Since my problem is still here... . I was reading that a diesel benz, when the valves start going out of adjustment it becomes harder to start, particularily when it gets colder out. Could the same happen with our cummins?

 

[PToombs]

Yeah, I've seen it on machines at work. You wouldn't believe a few thousandths out will hurt, but it makes a huge difference.

 

[DThibault]

I have the same problem with my 91, If I get it below a quarter tank or park it nose uphill with below a half, I can't get fuel to the engine. I did have some issues with the bracket holding the pickup breaking off and swimming around in the tank last year but I fixed that one. That was a weird one. I'd fill the tank and hand prime it. She'd start right up and I would drive it. Park it and go to use it again the next day no go. It would start if I ran it within an hour or two but not any longer. I think there must be a crack in the fuel line someplace as a result of that previous abuse. I will be taking the bed off when the weather gets better and probably replace the line to lift pump. For now, I keep fuel high in the tank and this winter I plow about 3 times a week with. This baby can push snow. We've got close to three feet on the ground up here and it keeps coming.

 

[ChrisWilliams]

Did you check the rubber lines going from the frame rail to the tank? Mine were real soft when I replaced all the fuel lines. Ten foot of 5/16 line is all you need to run from the tank to the lift pump to test it out. This would eliminate everything but the sump in the tank. It would be quicker to just pull the bed and do it right. You ought to be able to put in a draw straw and replumb to the lift pump for about $60 in parts. $60 won't even buy you a tank of fuel these days.