motor is a '97 12 valve cummins. problem is that it won't start unless i put a gasoline soaked rag on the intake. i checked fuel pressure at the injection pump and have 20+ psi. solenoid plunger snaps into the start position just fine. the problem started when i switched over to high performance injectors so i switched back to the stock ones that worked fine before hand. i even had them checked and cleaned. this is very confusing b/c once started.. it runs great. any sugestions would be great. thanks
fb

 

Did u check your air heater?

 

Thanks for the response, living in texas i figured as did others that the air heater would not effect starting, however I recall that the wire post for the heater was loose and turned on me when I had the air intake off last and I was going to test voltage and continuity on the heater tomorrow.

That it could be that simple, watch it be an sob to replace tho, thanks again, i will let you know how it turns out, fb

 

My $ is on an air leak.

Your engine will start just fine without the intake heater down to around freezing. Most non-cold days, I just skip the wait to start light.

 

i would have thought that an air leak would be both a start and a run issue, i have measured the fuel pressure at the injector pump and it is above 20 psi.

i suppose that could be 20 psi fuel and air.

is there any way to test for an air leak?? i have replaced the return fuel line, but it ran and started fine even when it leaked like a sieve ie no siphoning issues.

Thanks for your help, fb

 

20 psi is low, should closer to 40psi for the mechanicals. I would suspect either the overflow valve or the lift pump.I have done the whole fuel route on mine new rubber lines front to back,overflow valve, pulled fuel heater, ended up being the lift pump.

Copied this from a previous post of mine:
Been there done that,just finally got the hard start fixed this summer.You should replace all your fuel lines from tank to motor as previuosly posted,remove the fuel heater,check the pick up tube in the tank, replace the overflow valve and if it is still starting hard the lift pump. It was the lift pump causing the majority of my problem.
As a side note we actually have four filters in our fuel system,the main filter, the prescreen in the heater,in the tank there is a screen on the bottom of the pick up assembly, inside the pick up assembly there is another screen.
Found that one this summer when i pulled mine apart to check out the draw straw in the assembly.You have to seperate the bottom part from the top part to get to it but it is worth your time as a few guys have found theirs to be quite clogged up since they started checking them.
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Wrap an air blow gun with a rag and pressurize the tank, 10 psi max, and listen/look for leaks up front. Takes two people.

I use an old tank cap that I drilled and tapped a port into for an air hose. Makes it into a one person job. Also handy for filling and bleeding air from the filter after a change.

 

The most likely leaks:
-Fuel heater
-Rubber fuel hoses
-Anything you touched changing injectors (since the problem started at the same time, this would be symptomatic)

Often an air leak won't cause a problem after it is started, since the fuel system is under positive pressure.

Overflow valve pops in the high 20's PSI, IIRC.

 

Well here is the latest.

The air heater relay is out, however, it still will not start when the relay is bypassed out of the circuit. The coil has continuity and am certain it got 12vdc.

Pressurizing the gas tank; there is a massive air leak somewhere all you can hear is the rush of air going through the gas cap. I can not feel air anywhere so far; tried around gas cap, top of gas tank, lift pump, fuel heater, in desperation the exhaust, thanks again for any help, fb

 

There are steel fuel lines hidden along the frame rails under the cab FYI.

 

True and as such the last place to look, i will get my son to help later as i do not hear well anymore, thanks again for all help, fb

 

OK, now for the newest

pressurizing the gas cap, you would conclude there is a massive air leak somewhere, it is a balck hole for air, it never pressues up even in the slightest and I can not find where it is going.

While it is a brand new lift pump, i put a clear plastice tube directly to the lift pump intake stright down to a fuel can below and it will not draw fuel.

I believe this would have to mean a new lift pump unless there is something else i am not seeing, thanks, fb

 

Sure sounds like lift pump. Do you have any luck priming an empty fuel filter ? i know mine wouldn't before i changed it, now it takes about 20 pumps and you can here the overflow valve sqeal.

 

There is a vent in the pickup unit. During a roll over, it closes to prevent fuel spillage. If you are going to pressurize the tank, close that vent (its just a simple valve), or you'll never get any pressure.

Is there any blockage in the return line from the injectors?

 

ccmckee; i agree, i just can not beleive i am going to have to replace a brand new (100 miles) lift pump, but the primer will only lift about maybe one foot of head in the clear plastic line; doesn't look good.

Tate; please explain 'vent in the pickup unit', i am aware of a 3 leaf heart valve type valve at the bottom of the larger fuel fill tube where it enters the fuel tank itself; i thought this was to prevent siphoning (stealing) fuel. There is an air relief from the tank that joins high in the fill tube but before the fuel cap. i can not imagine what you are referring to.

The second question is interesting, the fuel overflow check spring is stretched out to insure fuel pressure to the injector pump, ithink i did measure upwards of 40 psi fuel pressure into the pump. i suppose a check valve set too high would be the same as a blockage, other than that the return rubber is new and i have no reason to think there is a phsical blockage. It would be easy enough crack the check valve if i could ever pressurize the fuel tank or alternately pull check valve and blow back throught the banjo bolt. i am not sure how this would keep the injectors from getting fuel.

Thanks again to one and all, i think we are about to get it, fb