I have been having problems with my truck all this winter, In Nov. I had cleaned teh whole fuel systems out(problems with water), the truck was fine with only a few issues. When I put fuel in the truck I don't fill it(don't have $100 laying around for fuel). It was fine up untill last week, it had gotten really cold(did it a few weeks before and I canhed the filter and it was fine then), and had trouble starting it. Yesterday I looked at it and and pened up the water drain on the filter and pure diesel came came out.

Once I got it started yesterday(forgot to plug it in and the batts. died), I went to take it for a drive and it died not even a few feet from my driveway, I got it started again and back it in my drivewya and let it idel for 10 minutes, I pulled out again and took off up the road and the truck ran fine.

One thing I noticed in teh course of me trying to get it started the fuel pump cut out and then came back on 30 sec later, I know most do this when they are primed,but the PO of this truck wired it direct so It is always on(when the key is on). Could the pump be shot after all the screwing with the water and what not? Could it not be strong enough to pump the fuel when it gets really cold(it was -25* some nights last week).

This fuel pump is on the frame rail right where the fuel filter is on the gas engines, I have loko and got a price of $100 for a new one online, is there any alternatives to the stock ones? Hell if I could Iw ould rather have a mechanical pump,but thats not possible.

sounds like a fuel delivery problem.

I would start by checking gph at the filter. remove the fuel line at the filter put it in a fuel can and turn the key to "run". after 10seconds check fuel level, there should be at least 1 qt. when the pump is freeflowing.

if fuel delivery looks good. i would check filters next.

if fuel delivery is low, i would check the screen on the pick up in the tank. there should also be a screen on the lift pump. if the screens get dirty everything will get messed up

BTW, did you add antijel to the fuel when the temps dropped, jelling fuel will cause some of the problems you are having.

sounds like a fuel delivery problem.

I would start by checking gph at the filter. remove the fuel line at the filter put it in a fuel can and turn the key to "run". after 10seconds check fuel level, there should be at least 1 qt. when the pump is freeflowing.

if fuel delivery looks good. i would check filters next.

if fuel delivery is low, i would check the screen on the pick up in the tank. there should also be a screen on the lift pump. if the screens get dirty everything will get messed up

BTW, did you add antijel to the fuel when the temps dropped, jelling fuel will cause some of the problems you are having.


The filter is only 2 weeks old on the truck, I will check the GPH this afternoon or tomorrow. I cleaned the screen on the pickup tube when I cleaned the tank and the rest of the fuel system. Screen on the lift pump? I have a inline fuel pump that i believe pumps right up into the filter housing, thats what my service manual shows.

Yes I add Antigel and more then a should to the tank, the only thing I am worried about is the place were I get my fuel does not move fuel that much(little town), the only place around that moves alot of fuel is the truck stop on the other side of town(25 miles away from my town).

While directed to the 6.5 a lot of what is here is applicable to what you are up against Lift pumps & OPS explained (http://dieselplace.com/forum/showthread.php?t=39350) you don't have PCM logic like 6.5s do but the 6.5 system is functionally similar to what you are describing, take a look at snot in my stocking linked in that referenced FAQ as well

Upon reading that I had a thought, that valve by the T-stat housing if I open that while running I will hearing it sucking air or what not but no ruel comes out, if I just turn the key to start i get fuel coming out of the valve.

Looking at that stuf what is the best way to test the fuel pump? Pull the line and see how much it pumps in 10 sec? The write up you posted Doc explains about the valves for priming the system. The plastic valve ontop of the filter block will drainfuel out with the key on 'run' and the pump running same with the 'T' valve up front, out of both of these the fuel does not squirt out fast it just runs out with a bit of pressure. If I have the truck running I don't get any fuel comeing out of the 'T' valve.

Looking at that stuf what is the best way to test the fuel pump? Pull the line and see how much it pumps in 10 sec?


Checking the free flow doesn't tell you much because the pump can appear to flow fine but be unable to build up sufficient pressure (and flow) under operating conditions. The best way is to put a pressure gauge into the fuel line going to the IP. Pressure to IP should be at least 5 PSI but not (much) more than 10.

The lift pump may have a built in screen you would find when taking it apart. It may be plugged, or the pump may have become too weak over time.


The write up you posted Doc explains about the valves for priming the system. The plastic valve ontop of the filter block will drainfuel out with the key on 'run' and the pump running same with the 'T' valve up front, out of both of these the fuel does not squirt out fast it just runs out with a bit of pressure. If I have the truck running I don't get any fuel comeing out of the 'T' valve.

There should be fuel running out pretty fast when the pump is running. That no fuel comes out of the drain valve (the T) when the engine is running indicates that the IP doesn't get enough fuel.

So you probably need a new lift pump. The stock ones are not very good; you might want to get a better one.

Quick question on the lift pumps, Is it at all possible to run a mechanical pump in my truck for now? The motor was replaced with a GM Goodwrench motor a few years ago by the PO.

Only reason I ask is I need to this truck tomorrow and the rest of this week, the only parts store open today told me 2 weeks to get a electric pump for my truck but they have a few mechanical pumps on the shelf for it.

OK well I just went out to the truck, I turned the key to 'run' and opened up the T valve and got fuel, I started the truck(started right up), and I got fuel out of the T valve again. The only thing is right now it is 23* and sunny and it feels like 30 some out which is a hell of alot warmer then its been the past week or so. Could it be that the pump just does not have the power to pump the thick cold fuel,but once it is warmed up it is fine cause it is thinner?

Still refer to my previous post above about the mech. pump.

P.S, There is no water in the fuel system, i took sample of fuel and let them sit outside and their was nothing frozen instead just straight diesel.

Yes, you could run a mechanical lift pump, but this problem isn't fully diagnosed. Here's what I would do...

1) Check for air leaks. You can do the air pressure test or you can install a clear line in place of the return line at the injection pump and watch for air bubbles passing through. If you have a leak, find it and fix it before you go further.

2) Check fuel pressure. This will tell you if the pump is running. For the little bit of pressure we're dealing with on one of these things (specs are 4-7 psi) it's generally good enough to open a bleed valve and see if there is pressure, which will tell you the pump is running (I suspect it is shutting off for some reason). Since you have an electric lift pump this obviously needs to be tested under several conditions, key in "start", "run", etc and engine running/not running. If you have fuel pressure just not all the time move on to the next step. If you have no fuel pressure move on to the next step. If you have fuel pressure all the time skip the next step...

3) Disconnect the fuel pump and test for power to the pump under the various conditions. If your pump is wired to an oil pressure switch this may not be possible. Alternatively, remove the lift pump and bench test it.

4. If you still haven't found anything, start checking the power supply to the shutoff solenoid on the injection pump. If that loses power due to a loose connection for any reason the engine will die.

I suspect that this problem relates to an air leak or some sort of problem in the power supply to the lift pump. It could have to do with the pump itself, but I sort of doubt it (and incidentally if the pump dies the engine doesn't usually die). Either way, whether I'm right or wrong, you should check it before you start replacing stuff.

Just occured to me... How cold are we talking here? If it was good and cold (really really cold) it may have been just plain gelled up...

Just occured to me... How cold are we talking here? If it was good and cold (really really cold) it may have been just plain gelled up...

Some nights it was -25* and during the day it was in the single digits, I could not see it gelling though just getting thick. I have double the dose of Power service in it at the moment. Would you believe I had none of these problems atthe end of last winter when I ran mostly off-road in the truck?

I went out and checked and I have no air bubbles at all, I have fuel pressure and also the pump runs at all times. Even when it was cold out I still had fuel coming out of my valves with the key in run,but it was think, with the truck running nothing came out of the T valve.

So basically it appears to lose fuel pressure when it is running, correct? Have you been able to tell if the fuel pump is running with the engine running (might be able to listen to it)?

How much flow do you get at the bleed valve with the engine off and the ignition in "run"? If fuel just runs out gently there is something clogged up most likely. I know you recently changed your fuel filter, but if you have contaminants of some sort you still might have issues with the filter being clogged. I would attempt to see if there is fuel pressure before the filter but after the lift pump with the engine running (crack a line open - be careful about it though as fuel can go everywhere - might be a good idea to have somebody ready to shut it right off) if you suspect this but don't want to go buy a new filter to check.

Does sound like you have some gelling occuring though. Heavy dose of anti-gel should fix that though (do make sure the additive you used has anti-gel - believe it or not some do not)...

Could it be that the pump just does not have the power to pump the thick cold fuel,but once it is warmed up it is fine cause it is thinner?


It could make a difference. I'm getting about 3--4 PSI when just running the lift pump and when starting the engine. After a bit of driving, pressure goes up to 5--6. I can't tell if that happens because after a short time of flowing fuel around it's easier to build up pressure or if it gets up because things are warmed up a bit.


Still refer to my previous post above about the mech. pump.


That probably won't work. There is a pushrod behind the pump mounting plate, sitting on the crankshaft, to drive the mechanical pump. Since your stock setup employs an electrical pump, you probably don't have the pushrod. Maybe even the camshaft is different and doesn't have the 'pusher' (How is that called?) on it?

So basically it appears to lose fuel pressure when it is running, correct? Have you been able to tell if the fuel pump is running with the engine running (might be able to listen to it)?


Another option would be to wire the lift pump yourself for testing. Get a fuse holder, a 7 amp fuse and some 10 gauge wire and hook the lift pump directly to the battery. Run a ground connection from the battery to the pump, too. Then run the pump and start the engine to see if you get fuel from the drain.


The 6.5s used oil pressure switches to turn off the lift pump when there was no oil pressure. These switches are known not to hold up well to the current the lift pump draws and could burn out.

Afair they had a setup to run the lift pump with the key in the 'run' position before the engine was started that bypassed the oil pressure switch. Once there was oil pressure, the pressure switch took over. When the switch was burned out, the pump stopped running.

Maybe you have a setup like this and your oil pressure switch is bad. To protect the oil pressure switch, you can change the wiring so that the oil pressure switch switches a relay which powers the pump.

Another option would be to wire the lift pump yourself for testing. Get a fuse holder, a 7 amp fuse and some 10 gauge wire and hook the lift pump directly to the battery. Run a ground connection from the battery to the pump, too. Then run the pump and start the engine to see if you get fuel from the drain.


The 6.5s used oil pressure switches to turn off the lift pump when there was no oil pressure. These switches are known not to hold up well to the current the lift pump draws and could burn out.

Afair they had a setup to run the lift pump with the key in the 'run' position before the engine was started that bypassed the oil pressure switch. Once there was oil pressure, the pressure switch took over. When the switch was burned out, the pump stopped running.

Maybe you have a setup like this and your oil pressure switch is bad. To protect the oil pressure switch, you can change the wiring so that the oil pressure switch switches a relay which powers the pump.


My pump is wired direct, you turn the key to run and it is on for as long as you have it to run, the pump runs when the truck is started. It is warm today and the truck runs great no problems what-so-ever, its getting enough fuel.


So basically it appears to lose fuel pressure when it is running, correct? Have you been able to tell if the fuel pump is running with the engine running (might be able to listen to it)?

How much flow do you get at the bleed valve with the engine off and the ignition in "run"? If fuel just runs out gently there is something clogged up most likely. I know you recently changed your fuel filter, but if you have contaminants of some sort you still might have issues with the filter being clogged. I would attempt to see if there is fuel pressure before the filter but after the lift pump with the engine running (crack a line open - be careful about it though as fuel can go everywhere - might be a good idea to have somebody ready to shut it right off) if you suspect this but don't want to go buy a new filter to check.

I would guess, It will sit there and idle all day long if I let it. When I got it running on Friday after i started it I let it idle for a few minutes and I took it ok and it died when I went to give it throttle. I got it started again after a little cranking and pulled it back in my driveway and let it idle for 10-15 minutes, after that I could not get it to die again,but it seemed like I did not have all the power.

Today I started it and took it out and I could smoke the tire thru 2nd gear with it, it ran great, I tok it up to 55mph and it seemed fine then. Today is close to 20* warmer then Friday.

Friday I had fuel coming out of the 'T' valve but only witrh the key in run ad it was thicker then what it is now, once I started the truck I had no fuel coming out of the 'T' valve.

When I had the truck running today the fuel came ut pretty good at the 'T' valve, it did not squirt out or anything though.

Did you get a sample of the fuel? Sounds like it is gelling up...

Did you get a sample of the fuel? Sounds like it is gelling up...


Yes I have to 20oz bottle filled sitting in the bed of the truck at the moment, I gues I could look at them tomorrow morning before I leave. Only thing is the low for tonight is 15* which is about 30*-40* wamrer then some of the nights last week,hell that even warmer then some of the daytme highs.

I wouldn't be surprised at gelling at those temps... :eek:

I wouldn't be surprised at gelling at those temps... :eek:

Yea, some nights last week were in around -25*f to -40*f, I had told the station owner where Iget my fuel(little store) thatI was having gelling problems. He told me the fuel is treated and should not gel no matter what, he would not listen when I told him they only treat the fuel to certain temps anything below there treatment temp it will start to gel.

I won't se how it runs today, I am taking another vehicle to school, I forgot to plug the truck in plus I don't feel like being stuck on the side of the road...lol, I don't think I could get the truck to repeat itsel;f unles it gets cold again.

our weather here doesn't get below 0f but go over the mts and you can find cold weather. diesel fuel really changes thickness issues from fifteen above 0 and fifteen below. all kinds of issues on gelling come out of the woodwork. hopfullly you will catch up with your vehicals issues you are on the right track just need to stick to it when the weather is cold cold.

our weather here doesn't get below 0f but go over the mts and you can find cold weather. diesel fuel really changes thickness issues from fifteen above 0 and fifteen below. all kinds of issues on gelling come out of the woodwork. hopfullly you will catch up with your vehicals issues you are on the right track just need to stick to it when the weather is cold cold.


Looks like this week is not gonig to work out it is suppose to be in the upper 20s all week ith lows in the single digits.

Even if the fuel is not gelling but it is getting think could that be a problem if the fuel pump is weak? I really don't know how many miles on on teh fuel pump, I can guess that there is 250,000 on everything but the body,engine,trans, rear frame.

If I need one the parts store in town can get me a Carter pump for $80

last winter i was having all sorts of fuel delivery problems. after adding some power service anti-jel(white bottle) all problems went away. i would add about 10oz to a tank of fuel.

any fuel pump will work just as long as you are getting at least 5psi, and 32gph. i prefer inline pumps because it's much easier to find somewhere it mount them ;)

last winter i was having all sorts of fuel delivery problems. after adding some power service anti-jel(white bottle) all problems went away. i would add about 10oz to a tank of fuel.

any fuel pump will work just as long as you are getting at least 5psi, and 32gph. i prefer inline pumps because it's much easier to find somewhere it mount them ;)

Thats the problem, i have about 10 gals in the tank and dumped about 16oz bottle in of the PS white, the diesel does not even smell like Diesel much.

Today I started the truck, it was 40* out, It started ruff but it was not plugged in. I let it idle for a bit and I went to take it up the road, it seemed sluggish. If i got on it from a stand still it did not take off like it usually does or like it did yesterday.

I don't know this truck is starting to piss me off, I am about ready to drop in the 350 crate that has 50,000 on it that I have sitting in the garage, plus with the way Diesel prices are if they go up anymore I am looking at $4.00/gal before summer.

Here's the thing... Diesel prices go up in the winter compared to gasoline due to home heating oil usage etc. In the summer they go down relative to gasoline.

It sounds to me like you might have gotten a bad tank of fuel somewhere...

Here's the thing... Diesel prices go up in the winter compared to gasoline due to home heating oil usage etc. In the summer they go down relative to gasoline.

It sounds to me like you might have gotten a bad tank of fuel somewhere...


Thats the problem I fileld up at three differant places and they all get their fule from the same supplier in town, I have yet to hear of anyone else with a bad tank.

I am going to pull the truck in the garage tomorrow before we get slammed with snow, i am goign to pull the fuel pump and see if the screen on the inlet is clogged.

With the prices, the one station onwer I talk to daily said they are expecting gas to go to 3.50+ a gal by May, which would send Diesel to close to or over 4.00/gal being that it is 3.80 at the moment.

Afair you need to take the pump apart to get at the screen --- and when you do that, the pump is broken. You can find some pics of pumps, including a stock pump, in a thread 'feeding the beast' in the 6.5 section. Maybe you have a different pump that can be cleaned. --- I'm still voting for the fuel pressure gauge, puts an end to the guessing.

What pump are we talking about here? I'm assuming the IP? I doubt it is that... Incidentally you can get to the screen on the IP without "breaking" anything for reference...

Considering the problems in the recent history I'm more inclined to think there may still be contaminants in the fuel.

As far as fuel prices go, my point was that diesel fuel doesn't go up quite so much in the summer as gas does... So if gas goes to $3.50 chances are diesel will still be about the same as it is now (obviously that varies from place to place but that's the general idea - gas goes up in the summer, diesel goes up in the winter - you get the idea). But that's a subject for another forum...

With the prices, the one station onwer I talk to daily said they are expecting gas to go to 3.50+ a gal by May, which would send Diesel to close to or over 4.00/gal being that it is 3.80 at the moment.


use WVO, then who cares what dsl prices are :)

My '85 was doing exactly what you are describing three weeks after i bought it. it took me another two weeks to figure it out. the thing was the guy i bought it from hardly drove it, it sat all winter with dsl in the tank. dsl will leave a sediment build up on the walls of the tank if let sit for too long. the sediment broke loose and clogged the screen on the sending unit as well as my inline filter. i couldn't drop the tank because everythig was so rusted on. i didn't feel like cutting it all off with a torch, so i cut a hole in the bed.

i used HS2500 method of pressuring up the tank, i pumped all 20gal out of the tank. then i cleaned the inside of the tank really well. installed new filters, filtered the dsl with my wvo filters, put it back in the tank, no more problems.

long story short. sounds like you ain't gettin enough fuel, either from a faulty pump or clogged filters. install a line pressure guage ;)

What pump are we talking about here?

lift pump

I talked to a mechanic and he said that there should be a screen right where the inlet tube screws in. I am still gogint o pull it off and bench test it, I am als going to pull the filter and the filter mount and clean that too.

Well I did not get to check it out, We had 10" of snow on Wed and I had classs today. I am going to work on it tomorrow and get it running, I made the decision tonight though that I am probably going to clean it up real good and put it up for sale. I did the math and I really need to get something with better gas mileage, so I am looking at 2wd S10 5spds and the like.

I am spending $100wk that I don't really have on fuel, and once I start colleg that price will go up cause I will be driving 300 miles a week.

It will be sad to see the diesel go,but gotta do what you gotta do, I will have one when I get out of college though.