Ford F-250 6.9l IDI - Riddle me this

[mankypro]

Here is a message I posted earlier on the Frybrid forum. I realize many of you don't care much about doing the WVO thing. I'm just hoping that someone could explain what could cause this behavior, regardless of the fuel used.

Ok. Just finished my v2.0 veggie conversion on my IDI - there was nothing wrong with the previous conversion, this one is just cleaner looking if a little troublesome.

Completely independent fuel systems until right before the IP.
WVO plumbed from the rear:

• Hotfox in rear tank.
• HoH to the CAT 2 micron diesel filter that is coolant jacketed.
• FASS 10psi pump
• HiH to the engine compartment/3 way valves.
• My setup is similar to GFS's "controlled return" with (3) 3 way solenoid valves.
• My return on veggie is looped T'eed to before the FASS (wvo) pump's inlet.
• After my valves I run both diesel and wvo through my FPHE - I switch to WVO when my fuel temps are 160F (gauge in cab).
• I have two sight glass filters - one after the FPHE and one on the IP's outlet.

Here are the symptoms:

• Runs fine on diesel, all the time.
• After running for a good 30-40 minutes on veggie oil - when I downshift to a light or just suddenly brake and come out of gear to idle it will cut off.
• Switching back to diesel resolves the problem after a few minutes of run.
• There are no signs of air entrapment anywhere and fuel pressure is in the 7-10psi range.
• The WVO tank shows no signs of vacuum - I drilled holes in the filler cap some time back to make sure.

I was thinking drain my veggie tank and toss the oil and run some diesel for a while with all the heat turned off to see if I can replicate the issue with cold diesel on the wvo fuel system.

The more I think about this the more I feel like something is wrong with the IP. Maybe the metering valve is getting fraked up with the veggie. The I-Pump is about a year and a half old, has about 15k on it.

 

[punkmechanic]

Could be crap in the veggie tank causing an inlet restriction. That would be a suction on the feed line, with no suction on the tank. Straight veg is filthy junk and it causes weird issues. Also our pump is set up to run a wide range of viscosities, it could just be the added thickness, coupled with the excessive fuel pressure is throwing it off. 10 psi is max for our pumps and they run way advanced at that.

hook up a vacuum gauge on your veg line and see if it pulls a vacuum, any more than 3 inches of hg is gonna give you issues (5 will work but it gets iffy around there). If no vacuum try dropping the fuel psi to around 5 and see if that has any effect.

punk

 

[Shadetreemechanic]

I think putting diesel in your veggie tank is a good diagnostic. My guess is that you have air intrusion in your veggie system, or you are correct about the metering valve.
If you are lazy (like me) you might just try topping off the veggie tank with diesel. That should cut the viscosity enough to free up the metering valve if that is the culprit.

 

[smolkin]

Was your IP a rebuild or new? Do you know if it has the old governor float or the new upgraded one? My old pump used to do that, and then one day the old-style plastic governor had enough of the veg and grenaded. You may want to check yours, look around the site for the correct way to remove/re-install the cover on the IP.
Since I put my new pump on, I haven't had this problem, but then again, I haven't run more than about 30 gals of veg through it yet, still working out the HIH setup and got sidetracked by suspension issues that demanded fixing. For some reason my aluminum fuel line in the HIH keeps kinking, what type of line is in yours? Home-made or purchased?

 

[jim_22]

I would bet it is under pressure at the IP (in spite of the electric pump rating) and the IP is pulling a vacuum on the 2 micron filter which is restricting flow. I agree as already suggested that you can test this easily by thinning out your fuel. Clear K2 (jet A) will be more effective than diesel for this.
PS Better yet (as suggest to me when I had lift pump problems, measure your fuel pressure at the input to the IP. Low pressure there eventually kills the IP.

 

[mankypro]

Could be crap in the veggie tank causing an inlet restriction. That would be a suction on the feed line, with no suction on the tank. Straight veg is filthy junk and it causes weird issues.

Agreed

Also our pump is set up to run a wide range of viscosities, it could just be the added thickness, coupled with the excessive fuel pressure is throwing it off. 10 psi is max for our pumps and they run way advanced at that.

I run a 23amp FASS on the veggie side, plenty of fuel pressure there as I'm instrumented with a pressure gauge.

hook up a vacuum gauge on your veg line and see if it pulls a vacuum, any more than 3 inches of hg is gonna give you issues (5 will work but it gets iffy around there). If no vacuum try dropping the fuel psi to around 5 and see if that has any effect.
punk

Excellent idea - the FASS is pushing close to 10psi - but it does this with the OEM pump as well - I know I swapped them. I'm thinking suspect fuel in the tank or the IP is going...

 

[mankypro]

Was your IP a rebuild or new? Do you know if it has the old governor float or the new upgraded one?

Reman - Pensacola supposedly with viton seals...no idea on the float.

For some reason my aluminum fuel line in the HIH keeps kinking, what type of line is in yours? Home-made or purchased?

Aluminum, no kink I was pretty careful about routing to avoid it. Home made.

 

[mankypro]

I would bet it is under pressure at the IP (in spite of the electric pump rating) and the IP is pulling a vacuum on the 2 micron filter which is restricting flow. I agree as already suggested that you can test this easily by thinning out your fuel. Clear K2 (jet A) will be more effective than diesel for this.
PS Better yet (as suggest to me when I had lift pump problems, measure your fuel pressure at the input to the IP. Low pressure there eventually kills the IP.

The 23amp pump (almost the size of the starter) is easily pushing 10psi as gauged right before the ip. The 2 micron filter is BEFORE the pump - it's pulling through it - pushing to the IP.

 

[smolkin]

Well, over here I can tell you that NO ONE goes to Pensacola Diesel even though they're less than an hour away...they have that kind of reputation locally. Not saying it's the IP that's giving you trouble but I wouldn't put it past PD to use old rebuild kits or something.

I used Test Calibration, a local Stanadyne dealer, and went with a brand new one to make sure it had the upgrades when I replaced my IP last fall. The new float material is supposed to last much longer with veg, so they say.

 

[mankypro]

Going to drain the veg tank, refill it with diesel and see what happens. The IP runs flawlessly on #2. So it's either the older veg in the tank or the IP when it gets hot wvo...


Going to toss a couple of quarts of ATF in the #2 tank and run it hard see if the metering valve is gunked up.

Well, over here I can tell you that NO ONE goes to Pensacola Diesel even though they're less than an hour away...they have that kind of reputation locally. Not saying it's the IP that's giving you trouble but I wouldn't put it past PD to use old rebuild kits or something.

I used Test Calibration, a local Stanadyne dealer, and went with a brand new one to make sure it had the upgrades when I replaced my IP last fall. The new float material is supposed to last much longer with veg, so they say.

 

[6 Nebraska IDIs]

It really sounds like a restriction problem. Are you filtering the veg? I'd check that filter to see if its plugged up.

 

[mankypro]

It really sounds like a restriction problem. Are you filtering the veg? I'd check that filter to see if its plugged up.

It does, but the filter is new and fuel is flowing at 10psi at the IP inlet - there is plenty of fuel.

 

[6 Nebraska IDIs]

Dang. That is really weird.

 

[mankypro]

Yeah I think it's either:

a. there is something going with the fuel
b. the IP is fraked 160f

Thinking of yanking it off and putting a new one on to see if it acts the same. Might be an excuse for a MWFI or a Moose.

 

[6 Nebraska IDIs]

Definitely go with the Moose. I sent in a brand new genuine Ford pump for my moose pump build and Mels guy even found problems with that pump! Its crazy the amount of detail this guy puts into his rebuilds.