Before I get a new lift pump...

[Sycostang67]

I'd like to get a second opinion. The last 3 days, my trucks has been cold starting differently. The first 2 days, it fired up and the idle surged for 5-10 seconds. Today, it fired right up and died, cranked it again and it revved pretty high and died again. The third try, after a few seconds of cranking, it fired up, surged for just a second and then smoothed out and ran fine the rest of the day. I have new viton rings, and all the return lines are dry. My lift pump appears original(125k miles) and looks moist. It's not leaking fuel, but dirt is sticking to it in a way that suggests very minor leakage. I am thinking air is getting in through the pump somehow.

 

[dyoung14]

Sounds like an air leak somewere

 

[Agnem]

Before you try to start it, spin off the fuel filter. If fuel comes out and floods the top of the filter as soon as the gasket comes free, then your not looking at an air problem. If the filter stays dry, then you have an air leak, and replaceing your lift pump will probably not help. Best time to do this would be after a lengthy shut down.

 

[fx4wannabe]

Before you try to start it, spin off the fuel filter. If fuel comes out and floods the top of the filter as soon as the gasket comes free, then your not looking at an air problem. If the filter stays dry, then you have an air leak, and replaceing your lift pump will probably not help. Best time to do this would be after a lengthy shut down.

Not to hijack or anything but I am still having starting problems myself. I have checked the fuel filter and fuel spills out as soon as the seal breaks so its full. So according to your statement that means no air leaks? I did this after the truck had sat for 3 days. My starts are still like I am losing my fuel prime. I am pumping 5psi from the lift pump and the glow plugs all check out. Timing is set to 7 degrees. I was starting to think that I was getting air in the system between the lift pump and the tanks. The check valve is what holds the fuel in the filter correct? Seems like if I was getting an air leak the truck would fire right up, burn the fuel out of the filter, then die.

 

[hesutton]

Have you tested the lift pump? If not, take the core out of the schrader valve on the fuel filter head. Hook up a pressure guage to that valve and crank the engine. It should be 4-6 psi. For volume, you should get 1/3 of a pint minimum with 10 seconds of cranking.

How old are the IP and injectors?

Timing is set to 7 degrees.

That's a bit retarded and that may play a role, but I doubt that's the whole story. Have you seen or smelled diesel under the hood anywhere our on the ground? How about the IP? Who'd you get your rebuild from?

Heath

 

[jim_22]

I am not an expert, but you might look at my post "air in fuel" because I had exactly the same symptoms as you do. I spent a lot of time trouble shooting and was aggravated for many weeks because the truck started and ran but it just was not right, and then finally it died. It was the mechanical lift pump, all along, a $57 part. In hind sight I see that it had been plaguing me a very long time, for more than a year: hard starting, what looked like fuel filter clogging, surging, bad performance at high rpm, etc. In my case the pump worked much better as the engine warmed up (probably due to easier flowing warmer fuel) and that made the diagnosis hard.

 

[jim_22]

Not to hijack or anything but I am still having starting problems myself. I have checked the fuel filter and fuel spills out as soon as the seal breaks so its full. So according to your statement that means

Be careful of the interpretation of that one. In my case, fuel also spilled out of the filter when the seal was broken BUT when I took it off completely as air bubbled out I could see it was really only half full with fuel sucked to the top and air on the bottom. Culprit: mechanical lift pump in my case.

But in my case, I checked the filter each time right after running the engine. When cold I bet the air would have risen to the top resulting in no fuel drip when the seal was broken.

 

[fx4wannabe]

Have you tested the lift pump? If not, take the core out of the schrader valve on the fuel filter head. Hook up a pressure guage to that valve and crank the engine. It should be 4-6 psi. For volume, you should get 1/3 of a pint minimum with 10 seconds of cranking.

How old are the IP and injectors?




That's a bit retarded and that may play a role, but I doubt that's the whole story. Have you seen or smelled diesel under the hood anywhere our on the ground? How about the IP? Who'd you get your rebuild from?

Heath

I do smell a little diesel which is why I think I have something going on between the lift pump and the tanks. I also have a problem with the pickup in the rear tank. I am pulling 5 psi at the valve on the filter head not sure on volume. I have been thinking about running an electric lift pump anyway and moving my fuel filter under the truck. I know my front tank is good as far as the pickup and sender so I am think about running a new line from just that tank to the new lift pump and up then I know that the whole fuel system is new and good to go. I would like to do away with the dual tanks anyway and get a big single but that is another thread. What do ya think?

 

[MIDNIGHT RIDER]

I can't seem to preach this enough :

The most important and useful gauge that you can install, before all the usual bells-and-whistles ones, is a simple mechanical fuel-pressure gauge.

Without one, all trouble-shooting becomes a process of elimination guessing game.

Furthermore, any rotary-type "vane-fed" injector-pump can and will draw enough fuel to run THROUGH a dead or dying lift-pump, with the operator being none the wiser; in this case, the injector-pump will have plenty of fuel to run the engine, but not the high volume circulating through the return system to lube and cool the pump, thus assuring it's early demise.


That being said, lacking a proper in-cab fuel-pressure gauge, check the lift-pump with a hand-held gauge and see what it is doing.

I have a very servicable fuel-pressure/vacuum test gauge kit that cost hardly ten-bucks at Harbor Freight.

 

[jim_22]

Good point, I am buying one today for under the hood checks. Will this one do the job?
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=93547

 

[fx4wannabe]

I can't seem to preach this enough :

The most important and useful gauge that you can install, before all the usual bells-and-whistles ones, is a simple mechanical fuel-pressure gauge.

Without one, all trouble-shooting becomes a process of elimination guessing game.

Furthermore, any rotary-type "vane-fed" injector-pump can and will draw enough fuel to run THROUGH a dead or dying lift-pump, with the operator being none the wiser; in this case, the injector-pump will have plenty of fuel to run the engine, but not the high volume circulating through the return system to lube and cool the pump, thus assuring it's early demise.


That being said, lacking a proper in-cab fuel-pressure gauge, check the lift-pump with a hand-held gauge and see what it is doing.

I have a very servicable fuel-pressure/vacuum test gauge kit that cost hardly ten-bucks at Harbor Freight.

Well I have checked the fuel pressure and I have 5 psi at idle.

 

[Sycostang67]

I'll check my filter today before I go anywhere. Once it's going though, the truck runs good as it ever does. The IP looks brand new, but my injectors are original.

 

[Sycostang67]

Well I had to leave in a hurry today so I didn't get to check the filter, but the truck started like normal. I'm wondering if it's just a fluke now. I dont think I will have to use it for the next day or two so I will try and check it before then.

 

[jim_22]

Ah, that is exactly what happened to me. First problem appeared a very long time ago. Some normal starts and some hard starts. Fuel light on occasionally for brief intervals (filter was new). Truck would run good when it was warm. Eventually got worse. Now I believe it was the lift pump all along, having a slow death. You know more than I did at the time because you have 5 psi now. All I knew is that fuel was flying out of the pump (at least when I checked it). I would monitor that fuel pressure. I think that the first thing that happens with that pump when it is dying is that is does not hold the back pressure so that the fuel filter drains (partially) when sitting for a long time.

 

[MIDNIGHT RIDER]

Good point, I am buying one today for under the hood checks. Will this one do the job?
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=93547

That is the exact one that has been serving me well for a number of years.


One other little addition that will prevent fuel drain-back and keep the fuel system from losing it's prime is to install a simple McMaster-CARR check-valve at the lift-pump's inlet; even better is to use two, with the second one in the filter's inlet. Any air or fuel leaks ahead of the check-valve(s) will not have any ill effect on starting .