1990 W250 difficult starting

[Ironforger]

Wow, first time ever for this. Truck has been reliable for years. Always consistently started right up with just a touch of the key, cold or not.



Now, suddenly one moring I go to start it up, it started for a few seconds then died. Tried it again, same thing. Tried it again, gave it some pedal then it started & ran fine afterwards. Good power idles fine.



Issue only occurs when attempting to start. Seems it will only start if I pump the accelerator pedal while cranking.



My first thought is fuel filter? Just picked one up yeterday, will try to install Saturday. Finally supposed to warm up here in NJ!

Fyi, I consistently use an anti-gel and it's above freezing.



Any tips or advice greatly appreciated.





Thanks!

[89dudney]

Maybe your idle is set too low? My truck used to do the same thing but when i turned the fuel screw in it raised the idle and it starts like a dream now.

[Ironforger]

I guess I can try that, but I'm not understanding why this issue suddenly begain. Truck never ever had such an issue before.

Where exactly is the fuel screw? It's been a very long time since I've tweaked this pump.

Thanks

[DodgeFreak]

Check your fuel pressure could be your lift pump quit. Is it the stock one??

[RCCUMMINS89]

You might have a fuel leak and the system is losing prime after it sits for a while.

[Ironforger]

Check your fuel pressure could be your lift pump quit. Is it the stock one??

I'm assuming it's the original lift pump. I've had the truck for about 7 years, and I'm the second owner. Has about 150k miles total.


I'll have to figure out the best way to check fuel pressure. How much should it be while cranking cold before the engine starts? It's a mechanical lift pump off one of the cam lobes, isnt it?

I have a new fuel pressure guage kit which I was getting ready to install on my 02 3500, been waiting for warmer weather. I can probably rig it up just to get a reading, I think I have an extra Tee laying around.


Otherwise I don't see any physical leaks under the truck & I don't smell fuel.

[RCCUMMINS89]

It doesn't need any pressure from the lift pump to start. However, if there is air in the lines between the tank and injection pump.... it'll fire up instantly and then bog down or die.

At idle... stock lift pump puts out between 5-7 psi... anything below 3 psi means lift pump is bad or going out. Or there is some sort of restriction in the system not allowing it to do its job.

[Ironforger]

It doesn't need any pressure from the lift pump to start. However, if there is air in the lines between the tank and injection pump.... it'll fire up instantly and then bog down or die.

At idle... stock lift pump puts out between 5-7 psi... anything below 3 psi means lift pump is bad or going out. Or there is some sort of restriction in the system not allowing it to do its job.

Thanks for the info.

My truck is the opposite. It does not fire up instantly anymore. It sure used to, then one last week I have to crank it and pump the accelerator pedal to get it to start. Once it starts, it's fine. Typical power as always and idles fine.

I'll see if I can check the pressure this weekend.

[RCCUMMINS89]

How long have you owned the truck? Is it colder now than when you first bought it?

[CumminsPower59]

It doesn't need any pressure from the lift pump to start. However, if there is air in the lines between the tank and injection pump.... it'll fire up instantly and then bog down or die.

At idle... stock lift pump puts out between 5-7 psi... anything below 3 psi means lift pump is bad or going out. Or there is some sort of restriction in the system not allowing it to do its job.

Thanks for the info.

My truck is the opposite. It does not fire up instantly anymore. It sure used to, then one last week I have to crank it and pump the accelerator pedal to get it to start. Once it starts, it's fine. Typical power as always and idles fine.

I'll see if I can check the pressure this weekend.

Sounds like a small air leak, allowing the fuel to drain back a little. Pumping the go pedal doesn't do anything, holding partially or fully open can help.

[Ironforger]

Sounds like a small air leak, allowing the fuel to drain back a little. Pumping the go pedal doesn't do anything, holding partially or fully open can help.

You could be right.

Finally a warm sunny day in NJ. Took a closer look and I see the top of the IP is slightly wet with fuel & it's running down & small drip off the side just above the Power Steering pump. Not sure where it's coming from. I'll try to take a better look at it this weekend. Maybe a quick pressure wash & dry, then run it to see where it's leaking from.

Thanks for putting me in the right direction. I hope it's something simple.

[Ironforger]

Well went to work on it today, couldnt get it to start at all.

So I took of the fuel supply at the Injection Pump. No fuel dripped out as I was taking it off. So I attempted to prime it with the push lever on the side of the lift pump and it's putting out foamy air bound fuel.


So Im assuming the lift pump is bad or a leaky supply line pre-lift pump. I may just change out the Lift pump since its original and very easy to change.

[depogrig]

Switch from the bolts to studs on the lp too while you're I'm there. It'll be easier.

[Ironforger]

Will do.

Just ordered the lift pump kit from Geno's garage. It includes a stud kit. http://www.genosgarage.com/REPLACEMENT- ... woWbc6mXuM

Gotta love Genos.

[depogrig]

I got my lp locally and didn't think to switch to studs. Oh well its on there now