Help diagnosing fuel problems?

[basilbowman]

Hey guys - so here's the deal.

About 340 miles ago I started getting fuel starvation issues. I'd be going up a hill and the truck would lose power and die, like it had a clogged fuel filter. There would then be a period of really having to crank on it to get it going again (mildly nerve wracking to have no start in traffic) and it would seldom catch, usually it would just start and die unless I really revved it up to 1800, and even then it wouldn't necessarily stay there. After swapping a couple of filters out, that wasn't the case, so then I changed the lift pump. That got me home from TN, but then the next day it wouldn't start. After sitting a day, it started, hard, and idled but wouldn't run uphill. The return lines were really rotted out, so I changed those last night, started it and idled it for ten, fifteen minutes, then started down the driveway, running downhill at maybe 1000, 1100 rpm to see if it would do anything, and yup - dead again.
Should I go get another lift pump? Is there a poor man's way to check the injection pump? How about the injectors, this couldn't be related to them, could it?

One more thing: When I had a buddy of mine turn it over while I pressed the relief valve on the fuel filter, mine hissed air at first, then spurted bubbly fuel, while his truck (same engine) had no hissing and clear fuel. This was yesterday before it died on the side of the road and I can't check it now because I don't have anyone to crank it while I press on the valve, so I don't know if changing the return lines did anything to help with that.

Any advice is greatly appreciated, I'm a bit at a loss as to my next move

Thanks,

-N

 

[DragRag]

Sounds like you could have a problem in your tank. The tube that goes down into the fuel may be rotted and broke off. Drop tank and look there.

 

[OLDBULL8]

Sounds like you could have a problem in your tank. The tube that goes down into the fuel may be rotted and broke off. Drop tank and look there.

That could very well be your problem, since it dies up or down hill. Less than a quarter of a tank it will do that. Either that or your sucking air from the tank line to the filter since you said you relieved air at the schrader valve on the filter. Your lift pump should be OK since a new one was installed.

 

[basilbowman]

Well, I can rule out tank problems - I had both tanks off and checked them when I set up my SVO 3,500 miles ago and they were both fine then. I then replaced the front tank pickup with a hotfox in tank heater, so that's brand spanking new, and the back one looked fine when I put it back. Also, it's a problem that occurs both on SVO out of the front tank and straight diesel on the back tank. What that does is eliminates everything behind the pollack (which I moved up underneath of my hood for shorter purge times). I pulled the check valve off of the filter head and it was bad, so I've got a new one coming in tomorrow. Maybe...

-N

 

[basilbowman]

So, new check valve in - still the same issue. I know the check valve was bad, but now it's doing the same thing, but at an idle, not even uphill, downhill or revving. I'm going to wipe down all the return lines from where I bled them after replacing them to see if there's a leak there, other than that, where else should I look? I'm going to check the lift pump, the pollack selector valve, I changed the fuel filter since it looked like there was some leaking there, then I'll just be stuck, since I don't know what else to do. Its coming down to crunch time, I've got to have this truck running by this weekend when I've got to go to school - how can I tell if an injector pump is failing, and does this situation sound like that might be a candidate? Thanks so much guys, I'm really grateful to have a resource like this. Cheers,

-N

 

[DragRag]

I'm saying no to the lift pump, it didn't fix your problem the first time. Does it die going up and down hill with both tanks or just one of the two tanks? Yes make sure the injector return fuel lines are leak free. If they are wet they are leaking, double check those. You could put a pressure gauge on the fuel line leading to the injection pump after the fuel filter, and if you have 4-7lbs constant then you know you don't have any fuel supply issues to the pump. If you are constantly getting good pressure which does fluctuate with a mechanical pump from about 4-7 in my experience then you need to start looking at the injection pump after that. Injection pump is always the last look, I always like to look at the stuff leading to it first. If you loose pressure then you need to go back in the system from there. You would need to be able to read the fuel gauge from the cab if it only happens while driving. if it does it at idle now, maybe you will be able to catch a low pressure read if it even exists.

 

[basilbowman]

The lift pump did get me home from TN, which was a drive of 300 miles with no issues. Never a stall or even a rough idle - I might go look up underneath an check that weephole on the lift pump to see if it's failed again, I know that the first one had failed and had cracked that diaphragm. (I need to change my oil too in that case, I'd forgotten about that) I think I might try pressurizing the whole system with a couple of pounds with an air compressor and a rag from the tank and looking for fuel leaks - I can't do any damage by doing that can I? Is there a weephole on the injection pump or something similar as far as a telltale for injection pump problems? I'm also going to check every damn connection I've ever made on there.
When I pulled the fuel filter off, it was about half empty, which means there's an airleak somewhere so that the fuel could be draining back down, but I've not pulled it since I changed the checkvalve, so it might have been that as the problem. I've got to go to work today, but tonight I'll tow it up into the shop and go to town on the *******.

The issue is existent on both tanks, at idle and 1.5k, uphill and downhill but is a faster stall when I'm revving the engine, not just letting it idle. It always starts after letting it sit for more than 20 minutes, but it'll start hard, usually on the second or third crank. Thanks for your advice,

-N

 

[icanfixall]

You might have an issue with the fuel tank switch over valve. Sometimes they stick and will not allow the fuel to return or draw from the tank selected...

 

[rhkcommander]

Locking gas caps? That was my problem once.

the ip isn't getting fuel. Does it happen on both tanks or 1? Both would probably be a clog or lift pump. One would probably be tank specific like broken pickup tube. Selector could be culprit too.

 

[idi traveler]

You move the selector to under the hood. Is there anyway that the line between the selector could be sucking air? Did you use new line or old? Clamps tight? Or anything that you haven't put your hand on twice?

 

[Compu Doc]

Since you are running WVO did you replace the return lines with Viton? If so did you use the proper clamps?.

If you did not replace them with Viton than you need to.

 

[basilbowman]

New information + additional thoughts...

First off, I replaced all the old fuel lines with the el cheapo diesel fuel line from AutoZone. I've heard bad things about it, but Dad's been using it with his Mercedes for probably three years now with no problems. Also, I'm broke and it was cheaper than Viton or the other lined stuff. I figure if I check both the lines and my filters regularly I can hopefully catch an issue before it becomes a problem and then replace everything. However, the only rubber that the WVO touches is about six feet under the hood.

The clamps on everything are locked down tight.

I'd driven about 3,800 miles on WVO without any problems before this nonsense started. I'm not sure about the selector, but I can check pretty easily, I'll swap out some of the rubber lines for a clear line to see what I can see as far as colors changing when I flip a switch.

----Important part begins now----

Today, I pulled off the steel line that goes from the lift pump up to the filter head unit. I looked at the rubber seals and they looked a little worn. As well, I nudged the right angle adapter that screws into the filter head unit and it moved with almost no pressure, in other words, it was really loose. I took the line and elbow into town and found a setup of a couple of barbs and two feet of hydraulic line to try to replace it with for now and set that up. I also re-seated the checkvalve and the shrader valve and put so thread sealant on them as well. Then I put a clear line from the check valve to the #1 Injector and cranked on it and watched the line. It spat bubbles for a while then filled the (return) line about halfway before it started. It idled and ran for a minute or two as I revved it, and didn't show any bubbles at all, but was still only about half full.
Then I took it out for a drive, just around the yard, and it drove about a minute before it sputtered, recovered for a second, then died. When I opened the hood, the return line was still at the same level, but there was a bit of fuel around the top of the filter head where the heater wire plugs in. I'm not really concerned about having that stupid heater, I've got three others on the fuel system so far (and more to follow) but I'm wondering if that's enough to cause a problem.
After supper I'm going to go out and swap out the line from the lift pump to the filter unit with clear line just to see if there's any air in there, so that I can concentrate my attention on the filter unit if need be. In the meantime, the supper bell is ringing, so I'll be back shortly.

Thanks for your help,

-N

 

[basilbowman]

Another thing I forgot to mention, after the truck died the return line emptied pretty quickly, and then when I started it back up to put it back in the shop it never filled back up, even when I let it sit and idle. That means that there was less air in the filter this time, right? The first time it filled up because the fuel was getting caught in the mix with the air that was getting blown out, but this time, since there was less air, there was less fuel to get mixed up in the air, right?

-N

 

[basilbowman]

Ok, so I just started it up and it ran and idled and spent two minutes at 1700rpm fine on diesel. I let it warm up and switched it over to SVO and immediately it started to show airbubbles, lots of them, in the line between the lift pump and the filter. I thought that meant a leak in the SVO supply, but then I remembered I'd closed the loop on the SVO so these could be recirculating bubbles that were getting worse as the truck ran more. I bled the air out of the filter with the Shrader valve, but I couldn't get rid of any of it.
Anyways, I flipped it back over to diesel and ran it a bit, still in the shop, and the bubbles went away, except for a few, very small ones.
I took off down the driveway, and a minute later it died. I hopped out, and looked at the clear line and it had some air at the top, like it hadn't quite filled up the tube. I got my dad to crank the engine while I watched, after the stall, and it was full of air as it came up from the lift pump. So, I'm thinking I'm going to take my new lift pump back and get another one and see if that fixes the issue.
What do you think? I mean, I was revving the engine pretty high before I started moving and not having any issues, and even when there were significant amounts of bubbles in the line between the lift pump and the filter it never sputtered or ran rough at all.
But, when I started rolling around the yard the line was almost empty. In a second I'll go try pulling the filter as soon as it dies, to see if the filter is empty.
What insanity! Wish me luck,

-N

 

[idi traveler]

I had some problems right after I got my truck where it would idle just fine, but if I tried driving it would die. I was laying under the truck chasing an oil leak and I looked up at the fuel pump. something just looked wrong. As I studied the pump I notice that the hose going from the steel line to the pump was collapsed. I turned the truck off and got back under there and it was round and proper looking. I thought that I must have an obstruction. When I reached up and touch the line it was like a sponge. The lift pump had enough suction to collapse the soft line. Replaced the line and fixed that problem.