infidel

It was bad until you stretched it but stretching is a short term solution.
Once it needs stretching it indicates the spring has lost it's springiness and will never be the same.
Replace the OF valve but doubt it will solve your problem.

Dhorn33

I ordered a new OV off Ebay today so I should have it in a few days. Not bad - $33.90 with shipping for a Bosch unit!

I plan to try to blow air through the supply line tonight and see if that makes any difference at all. I have also been told to check the ball valves in the LP and then I may have to drop the tank I guess.

infidel

Ball valves?
Never heard of them. There are two rubber check valves in the LP but they aren't replaceable unfortunately. When they go out it allows fuel to drain back into the tank when parked and can cause hard starting.

If you blow air back though the supply line it might clear things up for quite a long time. Make sure to remove the fuel cap first!.
The in tank filter is self cleaning by the sloshing back and forth of fuel in the tank. It takes some pretty funky fuel to plug it up.

66gaza

Have you checked the screen in the input to the lift pump? you can check it without removing the pump. I was in the middle of replacing my lift pump when I realised my original one was semi blocked.

Gaza

Dhorn33

I honestly don't think there is a problem with the lift pump. The truck starts perfectly (on an hill in either direction, on flat surface, etc.) and it seems to be able to generate plenty of pressure - it is just erratic and the guage is all over the place.

This morning I tightened up a bunch of hose clamps on the fuel lines (this truck has tons of clamps because of the wvo conversion) and on my way to work it was running mint! The fuel pressure was 30+ psi even driving down the highway - and it seems to be exacty where it was supposed to be. I could get on the throttle and it had the power it should - and it didn't stumble or hesitate at all. Then all of a sudden after one hard accelleration the fuel pressure guage dropped to 0 again and it seems to stumble a bit? Ugg.

I am now convinced that I should replace the fuel lines and try to eliminate some of the mess that the guy created when he installed the wvo system. I noticed that he still uses the stock metal fuel lines - then it goes to the stock braided line - then to rubber - then back to metal. He also had splices in both the return and supply lines using brass fittings and hose clamps. Finally - there are the 2 Greasecar valves that each of 3 connections and manage the supply and return lines and which tank is doing what. I am not even counting the additional fuel line that runs inside a coolant line to the wvo tank and that has several connection points too! In a nutshell there are at least 20 places where there could be air leaks and problems so I am suprised it hasn't given me grief before now.

I am seriously considering bypassing the wvo system, valves, etc and running new rubber fuel lines directly from the diesel tank to the engine and back in order to make sure everything with the engine and it's components is working properly. Once I get that straightened out then I might replumb the wvo system and see if I can get that working again.

Is it possible that once the overflow valve is replaced and the fuel lines are straightened out that my mpg will increase? The truck averages 15-16 with commuting to and from work and the highest I got was about 18.5 on an empty highway trip. I would love to see that go up obviously!

infidel

Low FP from a clogged filter will decrease mpgs so it follows that low FP from a bad overflow valve would do the same.
I've never understood the reason for a plugged filter to cause lower mileage but for sure know that it's a fact. Guy I know bought a new '95 about the same time as I did and never changed the fuel filter. It had 63k on it when his mpgs dropped to 17 on the highway. Just changing the filter got him back up to 22.

Dhorn33

Well I stopped by Napa over lunch today and picked up 12' of 3/8" and 5/16" fuel line - making sure it was rated for diesel fuel before buying it. I also bought some fuel injection style clamps and the total price for everything was just north of $36. I plan to replace the supply and return lines tonight straight from the tank to the engine. I was thinking about just leaving the stock lines in place and blowing them out with air - is this okay or should I remove them from the truck? I read about trying to prime the new lines by sticking my air compressor line in the tank fillup tube and cracking the bleeder screw up on the filter housing - will this work?

Baja

I think that blowing the old lines out and leaving them is fine though it may smell of diesel for a while.
From your last post the problem hit when you did a hard acceleration, meaning when the engine was really wanting fuel, it didn't get it. It got air too. Without question you have a air leak, really hard to find, especially with your WVO system. I know the drill, I have one too. You might take a clear in-line fuel filter and starting from the "out" side of your valves, hook it up. Get someone to floor it and look for bubbles coming through it. Keep going back until the bubbles stop. If you have no bubbles, move the filter forward. I once had a air leak and it was a real PITA to trace. The cheap hardware hose clamps tend to cut the line, be careful, there are better clamps out there. I used two clamps, opposing each other, for each fitting. Good luck, keep us posted.

infidel

That's the only way I do it. Even use this method to fill and purge air from a new filter after a change. I drilled and tapped in a air chuck into an extra fuel cap to make it an easier one man job.

The price you paid for the new hose seems way too cheap. Hope it's really diesel rated. Sometimes the counter guys think that if hose is rated for gas that it must be diesel rated.
I usually pay over $100 for 12' each of 3/8 and 5/16 marine diesel hose.
I quit replacing the short hose behind the engine a long time ago and started abandoning the stock lines running hose all the way from the engine to the tank. Besides being easier it's longer lasting and avoids future stock line problems that are all too common.

Dhorn33

He had the book open and according to the specs on their stand fuel line it is deisel rated? Am I missing something here?

I replaced the lines tonight and completely bypassed the wvo system for now. Dropping the tank was super easy - and the hardest part of the job is trying to get at the fitting behind the fuel filter. I struggled with that for at least 30 minutes and it was more than frustrating!

Anyway - I started it up and went for a drive and again I had some stumbling after a hard accelleration - but not every time? The fuel pressure is sitll erratic so I am still really hoping that the overflow valve helps out?

Dhorn33

Well - I drove to work today and the truck ran great. The fp was over 30 the whole time - but I never got on it hard.

My new overflow valve showed up so I installed it over lunch and went for a ride. FP at idle is 16-18 - and if I rev to 2500 rpm with no load it stays exactly the same? If I get on it while driving the fuel pressue drops to zero and I get the miss and white smoke out the exhaust.

The truck drives great - until I give it a lot of throttle then it just falls on it's face and the white smoke screen starts. ***?? What next?

HELP!!!

infidel

Sounds like your old OF valve was better than the new one.
I've heard tales that some are bad right from the get go.
With the wide range in prices charged for the OF valves you have to wonder.

Dhorn33

I will do the return line test tonight and see what happens - but assuming that doesn't indicate a bad OFV does this point to a failing lift pump?

infidel

If the pressure comes way up when you pinch the return line only problem could be the overflow valve assuming there isn't something restricting fuel flow at higher rpms.

Dhorn33

Pinched the return line with no change in pressure.

I stopped by Diesel and Import by my house in Blaine and talked with one of their techs. He gave me a few ideas - he suggested that since the truck idles fine with 18 psi and runs perfect at low rpm that it most likely isn't the lift pump but more likely some sort of problem with fuel supply before it. He suggested I cut the hard line between the pump and the banjo bolt and install some clear fuel line so I can watch for air. If I do this - how do I cut the line without getting debris into the line and contaminating the fuel supply? Is this a good idea?

One thing I thought I might try to test for problems with the tank and the pickup is to undo the new rubber lines I installed and run them to a temporary gas tank and run the truck to see if there is any difference in fuel pressure,etc. Good idea?


Oh - one last thing. It wasn't that long ago that I cracked open the AFC and slid the housing full forward along with sliding the stock plate full forward and turning the starwheel. I thought the truck was running awesome - but the more I think about it I remember having an issue where when I accellerated hard to get on the highway it would start to "bog" and studder at the bottom of the freeway entrance ramp. Is there any chance that me messing with this is causing any issues? Maybe the plate move backward or something? Just a thought?