Last January during a warm spell I ran a batch of petrodiesel / biodeisel (B33) in the rear tank of my truck. As the temperature dropped, I would get the expected FF Light activity and sense of loss-of-fuel to the engine, which was quickly corrected by switching back to the front tank (it only ever gets petrodiesel).

I'm used to seeing the FF light come on when requesting power if not enough fuel can be delivered.

Now things are different...

Rear tank has been running B100, front on petrodiesel as always. In some instances, particularly at high engine RPM (2000+) there is a definite loss of torque / acceleration (regardless of gear). I can induce an upshift, lowering the tacho, and get torque back. Forget WOT from a stop light as you'll never leave 2nd gear (if you leave 1st). Yet I never get a FF light while this happens. This phenomenon is much more significant when on the back tank.

I do get FF Light prior to start. It doesn't go away like the WTS and WIF lights will if you leave the key in 'on' position prior to cranking.

It's worth noting that I made a 5 gallon mix of dry, filtered WVO and gasoline (probably 85/15 or 90/10 ratio). The truck didn't like that, so I topped off the rear tank with B100 (12 gallons B100, 5 of shiite mix). I've finally burned through this today, but the problem I'm bescribing appeared about 1 week prior to the WVO/gas mix.

While buring through this tank, I changed fuel filter with no effect. I drained it 4 or 5 times for 10 sec with engine idling on side of road during a recent trip, also with no effect. Cold engine: worse problem. Warm engine: there is effectively an upper limit speed which I should not try to exceed cruise above or the issue will appear (grades obvoiusly exacerbate the situation). This ranges from about 48 to 62 MPH - haven't yet flushed out all the contributing factors.

Has anyone seen this 'inverted' FF light behavoir before? Also, any ideas why I get more torque at lower RPMs (so much more that even with the gear ratio change, the truck accelerates better).

thanks,

Rory

 

Rory, Check the FPR screen inside the right hand side of the fuel filter.

Rog

 

Could also be a dying fuel pump maybe. Because doesn't the pump have two sides and if the high pressure side was going then it would explian the loss of power at higher rpms.

 

I checked the FPR screen on the drivers side / top of the fuel bowl as kawa indicated...

Could barely see it for all the brown crap in the way - looked and felt like rust actually. Anyway, I sprayed a bit of brake cleaner in there, exposing the screen, but certainly not purging the crap behind it. What is the most effective, yet least labor intensive, way to clear it? Looks like one or two bolts and the inlet line is decoupled from the fuel bowl, no?

Rory

 

Generally just use a Q-tip with the cotton removed. Use the stick to scrape the crud off. There should not be any crud on the other side of the screen.

How ever, you can get to the other side by removing those two (2) bolts that you referred to But....be ever so careful as there is a tiny little plastic ball that will fall out and if it drops into the "Valley of Death" good luck in finding it.

Try scraping the screen clean, that works.

Rog

 

Mine was real ugly when my light came on. Cleaned it the best I could with a q-tip with the cotton cut off. New fuel filter. Been OK ever since. Changed the fuel filter yesterday
allot of build up again but no light. Might have to service it every few k before it clears up. Throw a new filter in it and see how it goes.

 

It got a new filter the other day, which is still good - I looked while I had it out today. I figured most of this stuff was coming from the tank side and not getting past the screen to the filter.

I'll have another look at the screen in a day or two. If it is jammed up again, I'll probably try to get behind it, being careful of the valley of death.

thanks,

Rory

 

Had a look in the fuel bowl. Screen seemed clean, certainly not as ajmmed up as it had been. Driving the truck more, new behavior has come to light.

No matter which tank I run on, I get get the loss of power / loss of fuel issue to appear. Just have to request enough power ie drive fast enough. In rear tank, the threshold is lower 45-65 MPH. In front tank it is higher, ~75 MPH. Fuels are different B100 (rear tank) is higher viscosity, so harder to pump. Petrodiesel (front tank) is thinner.

Could it be that I'm starving the fuel system to the point of causing cavitation in the injector pump, which then takes a long time to clear out?

Rory

 

I had my fuel pump go a few years back. WIth a load on, I could hardly do 30. Just nasty..... After a new pump, it was just awesome. If you've been pushing too much thick stuff through (especially with a weak pump) it'll wear out pretty fast. One last thing. There is the possibility that your suction screen in the tank has plugged off. Don't ask me how I know this. That was an ugly experience.............

 

I'd at least do a pressure test at the shrader valve on the side of the fuel bow, might need a second set of hands (feet) to run the pedals to get er spooled up..... definately sounds like a pump issue......

Slick!

 

I'm really leaning more towards the lift pump. Looked at ODB data while driing and I can comfortably drive 3-4 [cc/sec] of B100 and higher (didn't try for the limit but I suspect 6+ [cc/sec]) on petrodiesel.

Question 1: is the lift pump located before the filter or bewteen filter and injector pump? I'd think it's before the filter but somehow reading in other areas I got the idea it was after the filter.

First quote I got on a lift pump was $400 or $600 or something (seemed way too high so I kind of stopped listening).

Question 2: Any reasons not to run an in line electric pump located just past the fuel selector valve to help deliery and (maybe) avoid replacing the stock lift pump?

Rory

 

Go to IH. I paid $150. It's a 2 stage pump. Lift pump and low pressure pump.

 

Mine was around $125 from NAPA

 

I found a BOSCH fuel pump for $80. Bought it and installed Friday using posting by sam miller (found in another thread) as a guide. Took about 4 hours. Solved the problem. ODBII data indicates I can push upwards of 13 [cc/sec] of B100 without issue.

Rory

 

I found a BOSCH fuel pump for $80. Bought it and installed Friday using posting by sam miller (found in another thread) as a guide. Took about 4 hours. Solved the problem. ODBII data indicates I can push upwards of 13 [cc/sec] of B100 without issue.

Rory