I'm going crazy!!!! A few weeks ago I was running just fine on WVO and when I went to switch back to diesel the truck died within a few seconds. I've been over everything I can think of with the tools I have (limited budget) and I feel like it should start, but no fire! Please Help!!! Here are the details.

Potentially pertinent history:
I ran out of gas a month or so ago. Both fuel gauges don't work. I know running out is a no no, but I messed up. In the process of getting it running again I killed the starter. Replaced that and it fired right up. New starter seemed to crank faster than the old one. Got 2 new batteries (a few months old). Lately I had been noticing the tach doing funny things. It was maxed out when driving down the road at 30mph but clearly the engine was running normal rpms. After warming up a bit it seemed to smooth out, but would still jump around occasionally. Now the tach doesn't move when cranking. Also, the last time it ran well I had a hard time getting it started (5 or 6 cranks, then good to go once running). The Veg is heated in 3 places: tank, veg filter, and veg. therm in line just before it hits the IP.

What I've tried:
This truck is a hobby for me and I work, "off the grid," every other week so it only gets driven a few times a month. At first I thought there may have still been air in the lines from the initial run out. I cranked and cranked while cracking each line (except for #1). I also tried squirting liquid silicone into air intake to get it to run a little and save some cranking. It would occasionally fire for a few seconds, running real rough, and then die. When it did fire there was no response when pushing pedal to the floor (sounds like a definite fuel problem right?). I've changed the fuel filter (I filled it with diesel) and then bled the lines again. I tried running a hose from IP intake directly to a can of diesel... No start. I disconnected the fuel line into the fuel filter and cranked for 10 seconds. Plenty of fuel. Question: I don't have a pressure gauge, but I assume if I get at least 1/3 pt the lift pump is good. Do I need to test pressure there too? I reconnected that line and did the same test with the line coming out of the fuel filter. Plenty of fuel. Just to cover all the bases I tested all the glow plugs. I did a resistance test with them still in the head and got 0.7 ohms or less on 6 of them. The other two I replaced. I tested voltage at all glow plugs and got about 9.6 at all 8. Glow stays on for about 10 seconds at on first glow. When I had each line cracked I appeared to be putting out plenty of fuel, but I don't have much of a reference. It's more than a few drops though. Does anybody have a good video of what it should look like? I have many of the fuel lines replaced with clear. I have no bubbles that I can see going into the IP. I have cracked and bled the lines quite a few times at this point. I do have a few small bubbles in the return line after each crank. A friend told me this was ok. I'm assuming it comes from when the injector pops open and closed. Question: When retightening the steel injector line on #8 there seems to be a 1/16" gap between the nut and the plastic return line cap. This looks off, but I can't seem to get it any tighter/ don't want to over tighten. I've been seating the nut and then about a 1/4 turn. I tried a bit of wd-40 the threads, worked it back and forth, more wd-40, a bit of brushing, back and forth, and so on. Still stops at same place. Is this normal?

What I'm thinking

It sounds fishy that it died when I switched fuels. I am assuming that the 1/3 pt per 10 second crank tells me I'm getting enough fuel going into the IP. Is this a safe assumption? As I was writing this I just thought about the o-rings in the cap that everybody talks about. I would do the return kit, but with my limited funds I don't want to go buying stuff that I MIGHT not need. If the O-rings are worn could this cause the cap to sit lower, creating the 1/16" gap? Would this cause a not start? I also watched a video where a guy cleaned the check valve on the return line to the IP. Gonna go check the O-rings on the #8 cap and maybe clean the IP return line check valve while hopefully somebody responds!!!! Thanks for reading all this. I tried to be detailed in my first post to avoid too much need for back and forth. I was told when I bought this truck that WVO would eventually kill the IP. I'm hoping that's not the case. How can I test the IP?

 

I love how detailed you are in your post, but you forgot some crucial info:

What year is your truck? What engine? Turbo or non-turbo?

I think you have two problems. One is an electrical issue, giving you some strange behaviors. The other is a fuel issue.

If you have an older engine, like a 7.3IDI or 6.9IDI, you might be encountering the dysfunctional electronics with a bad voltage regulator (if you have an external regulator). I had all my gauges and other electronics running weird when my external regulator went bad, and also it started poorly like yours did.

I think the fact it died when you switched over is just a coincidence. With that and your electrical problem, it compounded your situation. Too many people have run WVO in these trucks for too long for us to hear the typical complaint "You run WVO in there, it'll destroy your IP." BS. But if you haven't properly filtered and dewatered your WVO, then you could have problems--however they are gradual like the pitting of injectors, polymerization of the IP/Turbo, etc etc. That is not what you have.

Next question i have is, what WVO system do you have? Also, What selector valves are you using? Your symptoms are very very very similar to a problem I once had 3 years ago on my Jetta. I was running two Hydroforce valves, and one day I went out to drive the vehicle and there was no fuel. It would crank forever. After checking everything, I found my selector valve plunger was stuck exactly between the two openings, so no fuel could get thru. You might want to check that.

But you tried running it on the diesel can and that didn't work, bypassing your WVO system. That's hard to figure out. If it can't run from a can of Diesel, then I'm not sure what to say. I don't think this is a glowplug issue because unless you are in a very cold cliimate, it should eventually startup without GP assistance, just from the pressure of the engine.

you are getting fuel if you bypass the diesel filter, so your lift pump is OK, the diesel selector valve is OK, and the diesel fuel lines are OK.

It might be an IP issue. Hard to say. I'm not even sure about which engine I'm writing.

 

Thanks for your response and support! It's an early '94 IDI non turbo. I'm running a greasecar system with some modifications. I have three valves for diesel, veggie, and purge mode. I'm about to go off the grid/unable to email or work on my truck for a week so I'll have to put things on hold. I just ordered a injector return line kit that should be at my house when I get home next Wednesday. That was a fairly inexpensive thing to try and all the return stuff looked old and rotten anyway. I'm gonna check the check valve in the return line to the IP next week. I saw in a video that debris in that could be an indicator of a failing IP. Stay with me. I'll be back in a week! See you then!

 

No prob. Repost once you get back on the grid.

 

So it took a while, but I finally got around to installing the fuel line return kit and WOOOOOOO HOOOOOOOO!!! Fired right up! Got a couple of questions though. It runs fine on diesel. When I hit the switch to go to veggie it died. I could see the veggie lines full of air, so I kinda assumed that I had just gotten a bunch of air in the veggie side during all my diagnostics. I switched back to diesel, cracked and bled all the fuel lines at the engine, and just like I thought, fired right up on diesel. Now here are my questions:

1) I can see a bunch of tiny bubbles (looks like white foam) in the return lines, starting after the kit I installed. After shutting down and letting it sit, the bubbles settle and the lines are full of fuel (no apparent bubbles). I have my system set up to have a purge mode that will cause it to run on diesel and route the return fuel back through the veggie system to backflush the veggie system before shutting down. I'm hoping the bubbles are just air in the return lines from my replacing them, and I can just run it on purge, flush it back to the veggie tank, and everything will settle out. Does this make sense to anybody or does it sound like I still have a small leak somewhere in the return system? I'm tired of dying and bleeding to restart!

2) When I put the replacement fuel return kit in I pushed the little plastic caps down as far as they could go. Most of them felt like a little, "click," into place which I assume was the o-ring seating in the groove inside the plastic cap. However, now each cap has about a 1/16" gap between the top of the cap and the metal nut that holds the fuel line on. Before I took the old caps off, most of the caps were flush with the metal nuts, except for one (which had the same 1/16" gap as all of the current caps). I'm not sure which is correct. Did I push the caps down too far? Could this be the cause of the bubbles in the return?

I could figure this out on my own, but I've been working on this for so long that the idea of another session of trial and error is unapealling. I'm hoping someone might have some guidance.

3) Finally, do I need to replace the lines that came in the return kit with some other material to run veggie?

Hope someone is still listening!
Thanks!

 

As for the bubbles on your return lines, I'm not sure how that's happening. All I can say is, try to install your sight glass closer and closer to the return lines, so you can narrow where it's coming from. You could have a cracked hose somewhere, it could be leaking from the return bib on the diesel filter, it could be a variety of things. I never understood why the return line would ever have air in it, nor why that would even matter for these engines, since the return system isn't pressurized and should contribute to the stability of the engine, but apparently it does matter. When I look at the fuel system diagram in my Ford Service Manual, the return system could be full of air, and it shouldn't impact the performance of the vehicle.

Now that the air bubbles are backflushing with your diesel, i can see how that would be a problem for your veg system.

I think all you can do is narrow the point at which your diesel return system is finding air, then replace that hose or component. How are you bypassing your diesel filter head return bib back to the diesel return system with your veg system selector valves?

Are the bubbles consistent? or do they eventually go away with revving or do they get bigger or more frequent with revving? Strange... on the return hoses... i've only ever had bubbles on the supply side, and that was from a crack in a hose on my Jetta. It was sucking in air.

 

Try a fuel pressure gage close to the IP in the Vegi oil line to make sure your getting vegi fuel. If your not getting vegi oil go back to where the pressure stops. Might ba a bad pump. Since your using a back flushing in your setup, that might be where the air is coming from and you might be pumping air into the vegi oil side. Try to block off the flushing part of your system and see what happens.

 

only one way for air to get in the fuel system if the tank is full and the fuel pick up is good, a leak on the suction side of the system before the pump, the original fuel filter system on the idi has a small orifice and check valve leaving the filter head that removed air from the system and put it down the return line system and back to the tank, air would be picked up from sloshing of the fuel tank, your system probably doesn't have this feature, so any air must go thru the Ip. you must have a bad fitting on suction side of veg system.