hey..im sorry about your luck. Heres what i have learned.

1.Only use the stock lift pumps for the truck, mine reads 11psi on veg.

2. My return is Teed about a foot before the lift pump.

3. I rewired my pumps to bypass the OPS. I have a toggle switch I have to switch for veg and diesel pumps.

4. My filter is a coolant heated hot head with cooland wrap.

5.The truck will run without a steady fuel pressure, just not much power, and surging.

6. I have one pump before, and one after the veg filter.

7.No fuel goes unheated

8. NO POWER SERVICE PRODUCTS!! POLY!!!

9.I get about 28 mpg with my 94 k3500 crew cab long bed with fuel miser chip.

10.The belts could be a problem with battery voltage. When my alternator went, the fuel pressure completely went to zero way before the truck died.

11. I use only Fleetgaurd fs1000s, or napa and donaldson crossovers. Any smaller filter makes it tough.

Hope these are useful

quote:

If I crimp off the hose leading to the IP I get full PSI (static system) with the engine off and the pump running. This works for any of the pumps 7 psi walbro or 10 psi gm. With the hose not crimped I get much lower numbers. But I used to get full pressure readings with the hose not crimped. So flow is going through the ip to somewhere and the system is not static with the engine off! But the ip has NO EXTERNAL LEAKS, no diesel in the valley (I fixed a leaker injector return that was causing the diesel puddle). So fuel must be heading down the return.

The HPCA valve is probably stuck open on the IP. This solinoid opens up on cold start and allows dome pressure to drop to zero, thus advancing the timing. At 130 degrees, this solinoid closes the valve and the valve pops open only at operating dome pressure (4PSI I think). If you are getting flow with the engine off, then the valve is stuck open. Even with a new lift pump, filling the dome without the IP rotating is very difficult as the only direct flow is through the vent orifice, internal in the pump.

Another possibility is the trailing port snubber in the cone section (where the intake line goes in) may also be stuck open, though you wouldn't see any difference unless the pump was rotating.

Bill

For the curious, here is the latest chapter of the drama including another (an the biggest so far) sleep-deprived stupid trick.

We're all back home safe in Lubbock --- my wife, the dogs and I. The truck is in Albuquerque and at least it is an easy place to fly to on Southwest and I have some air travel coming up anyway.

On friday night a friend of mine visiting his brother in Taos (we were supposed to meet up in Taos on this trip) had to drive his mother to the Albuquerque airport, so he just drove the hour down to Socorro to meet us and provide us with plan c backup to get us to the national car rental agencies in Albuquerque and home.

He and I did more diagnostics. Pumps are pumping well and receiving power when engine is off. But fuel is free flowing to return. So we are very sure it is the ip and Bill McD's hypothesis seems most plausible. We decide to do one final test to check the hydraforce valve that controlled the return with the engine idling and I jump in and turn the engine over, forgetting that I have the air cleaner off and paper towels over the intake. At least one was sucked in on the driver side . . . thump thump.

No real sleep since Monday night = dead brain. So now I probably have damaged valves/guides/rods. Well, that at least made the decision to go to plan C easy: Truck flatbedded and to diesel shop in Albuquerque.

I'll post back on the verdict. I was beaten fair and square this time. First time I've not managed to get a vehicle home.

Thanks all for your help and ideas. Nate Powell, I'll keep what you've learned in mind when I set things up again. Well, that is down the road from now.

Thanks,

A plain paper towel sucked into the intake shouldn't be enough to cause damage, in my experience. There should be enough clearance between piston and (cold) valve for normal carbon buildup, which is roughly the same thickness as a paper towel. Not all of the towel will enter the cylinder, anyway - only a portion will find it's way past the valve, then get pinched off when the valve closes and the piston pushes it down to the seat (making bad noises).

I've seen old-style diesel engines started in very cold weather by stuffing a newspaper into the intake manifold, lighting it with a match, then cranking the engine over, sucking the burning paper into the engine. Granted that those weren't GM V-8's (they were big Mercedes truck engines), so I reserve the right to be wrong about this, but don't jump to any conclusion until you at least do a blow-down or compression check - those will show up a bent valve, if you have one. I hope nothing got damaged.
Bill McD: would the engine run normally if the entire fuel loop were pressurized to 4psi, even with the HPCA valve stuck open, or is there any other way to limp home with that sort of problem? If so, that would be a good thing for 6.2/6.5 owners to know.
Cheers,
JohnO

Johno:

If the HPCA is stuck open, the timing is advanced as it would be during a cold start. Limping home with it advanced should not cause any long term problems. As far as pressurizing the return system, this would be an excercise in balance. Too much and the engine stops (have used this on occassion to stop a runaway engine by pinching off the return) and too little you return to advanced mode.

Dome pressure is controlled through the HPCA valve that acts as a pressure relief in run mode, keeping dome pressure at a constant value (tried searching through my old manuals but can't find the exact figure but seem to remember 4 PSI). Timing for the engine is established based upon the difference between transfer pump pressure and dome pressure. As engine speed increases, so to does transfer pump pressure. As the dome pressure remains constant, transfer pump pressure forces a piston to advance the timeing.

Anything that effects these pressures (viscosity, fuel return restrictions, temperature etc.) will directly effect the timing. There are a number of internal components designed to maintain a constant relationship such as the trailing port snubber (to compensate for viscosity) and the vent wire orifice, but they have their limitations.

Hope this is of some value to you.

Bill

So what ever ended up happening with the truck? Did the paper towel indeed cause serious damage? Did you ever diagnose what happened with the fuel system?

Hi Folks,

I have been super busy with field work, a new research program, a kid on they way, and working on the house which all left no time to deal with the suburban. But I thought I'd update all those folks who helped me out last fall:

The blue shop towels I sucked into the intake did mess up the valves. Then a cracked head was discovered upon that repair. The engine rebuild company finally sent a new and definitely uncracked 6.2 head under warrantee. Either the head was bad on original rebuilt engine or a short overheat during my conversion build last year caused that. Due to having no time, I had a diesel shop in Albuquerque do that work and rebuild the ip.

The IP was shot as suspected. If I had not messed up the valves in my stupidity I probably could have limped home with the temporary fix I was working on. But then we did discover the cracked head this way and have nice new heads well-checked by a machine shop. With a rebuilt IP on the truck ran great! (on diesel for now!).

Belt issue has been a separate headache. After fiddling with brackets and shims and finally getting a new main pulley, it seems fixed for good. Fingers crossed.

Truck runs great and looks gorgeous, it just ended up costing a lot more than originally planned. a lot cheaper than new, but more than an old chevy should cost. Its only money.

So, I'm thinking about re-installing the veggie system. But I'm paranoid about ruining an ip. I don't know why the last one failed, but it may have had nothing to do with vegetable oil: it was of unknown age (I foolishly did not replace it when I put in the rebuilt engine) and it had sat in the blown engine in the desert for a few years. Before proceeding, there are two issues I need to deal with:

1) I had placed my FPHE right before the T and check valves where the 2 fuels join just before the IP. This is great because there is essentially no cold veggie anywhere and also because it is all brass fittings from the FPHE to the T some heat is transferred to diesel fuel which is not cold upon switchover. The downside is there is no filter between FPHE and IP so I plan on putting a 30 micron or so clear filter before the IP. I need to find one with glass and metal only as this will reach almost coolant temps. So far, the ones available locally have plastic.

2) I had looped the veggie return to the inlet side of the veggie lift pump and this caused negative pressures on return lines on veggie fuel. Only solutions seem to be either put a needle valve in the veggie return to allow adjustment and pressure could be slightly above atmospheric, or redo plumbing so veggie is returned to tank. If I put a valve in, will one setting work for different engine speeds and loads?

Meanwhile, I'm running on diesel and trying to get over my fear of this vehicle. We had to think hard about sunk cost fallacies recently . . . and doubled down. And I had to drive my 1990 gas ford F250 for my California field work all summer.

We'd put a lot of work into the suburban--- I sprayed in bedliner in the cargo area, rebuilt the seats, replaced dashboard, fixed the ac, put in stereo and vhf radio, etc

Thanks again to everyone for the help last year. If you are coming through Lubbock, I have lots of vegetables in the garden!

This message has been edited. Last edited by: Pulaski,

quote:

I need to find one with glass and metal only as this will reach almost coolant temps. So far, the ones available locally have plastic.

These can actually be heated to near coolant temps too with a coolant wrap.
I have run tens of thousands of miles with a plain old cheap Fram plastic cased disposable rigged in this manner.

quote:

2) I had looped the veggie return to the inlet side of the veggie lift pump and this caused negative pressures on return lines on veggie fuel. Only solutions seem to be either put a needle valve in the veggie return to allow adjustment and pressure could be slightly above atmospheric, or redo plumbing so veggie is returned to tank. If I put a valve in, will one setting work for different engine speeds and loads?

I don't understand how placing a valve between the return and the lift pump will negate this problem. How will this reduce the cance of negative pressure developing?

quote:

Originally posted by danalinscott:

quote:

I need to find one with glass and metal only as this will reach almost coolant temps. So far, the ones available locally have plastic.

These can actually be heated to near coolant temps too with a coolant wrap.
I have run tens of thousands of miles with a plain old cheap Fram plastic cased disposable rigged in this manner.

Ok, yes, I have read posts where folks do this. I was worried since this will be right before the ip. I had visions of melted plastic in my expensive rebuilt IP. If I can find a good option, I don't mind spending a few more dollars for piece of mind. JEGS had some aluminum housing and metal screen filters I saw, but not clear,of course $30 vs the 10-15 for the plastic element type. Locally, all the places carry a Mr Gasket or similar glass filter with plastic mesh filter element.

quote:

quote:

2) I had looped the veggie return to the inlet side of the veggie lift pump and this caused negative pressures on return lines on veggie fuel. Only solutions seem to be either put a needle valve in the veggie return to allow adjustment and pressure could be slightly above atmospheric, or redo plumbing so veggie is returned to tank. If I put a valve in, will one setting work for different engine speeds and loads?

I don't understand how placing a valve between the return and the lift pump will negate this problem. How will this reduce the cancel of negative pressure developing?

Idea (as suggested by Scott McPhee back when I was stranded) was that a needle valve could be used to increase resistance in the looped return so that the ip return outlet and injector return lines see a pressure slightly above atmospheric to mimic resistance back to tank (which itself is at atmospheric) under stock return scenario. The needle valve would be between the 3 port valve that directs return flow either to stock tank (on diesel) or to just before the veggie lift pump (on veggie). I'd need to put a gauge in temporally to measure pressure in the return before this valve. The idea is to avoid malfunction or damage to ip resulting from having low pressure on the return outlet and to avoid air entry into lines that low pressure on injector returns might cause.

I'm trying to do things as close to perfectly as possible! My current veggie setup is great in that the temps are very hot with the looped return (perhaps too hot? around 180F measured just before the last hose running to the ip) and there is no place for cold veggie to sit since the T where veggie line meets diesel line is attached to the FPHE. The T also provides some heating of diesel which discussions suggest may help avoid temperature shock to the ip. On my wife's mercedes I use injector line heaters which are nice since that heat is post ip. But given the other electrical loads on this 4x4 and the fact that I have plenty of engine heat, I'd like to use just coolant heat.

quote:

I had visions of melted plastic in my expensive rebuilt IP.

Even the $3 Fram disposables (clear shell/paper element) don't come close to melting at coolant temp.

quote:

Originally posted by danalinscott:

quote:

I had visions of melted plastic in my expensive rebuilt IP.

Even the $3 Fram disposables (clear shell/paper element) don't come close to melting at coolant temp.

Thanks, good to know. So that is a strong vote not to worry about inline filter disintegration between FPHE and ip. So that solves one issue. Now I just need to figure out best solution regarding looped return on this vehicle.

Just to clarify for folks and hopefully make these posts more useful to searchers:

This issue of looping the return is problematic with these Stanadyne IPs. Despite prior research, I didn't understand how these pumps control timing through pressure differentials. Looping the return with my nice mercedes ip was not an issue (actually I set up the 300D with a manual valve to choose looped or return to tank). There is discussion of this issue with similar IPs on the forum (eg http://biodiesel.infopop.cc/ev...1083921#8821083921), but I missed the issue in my original design. Problem is that looping to after the lift pump of course pressurizes the return and looping before lift pump reduces pressure below stock. Using a return to veggie tank is one solution but has two drawbacks: more heat loss from fuel and the related issue of heating fuel in the tank and perhaps encouraging polymerization.

The SAME THING happened to me using this same WALBRO pump FRB 7-10psi
worked two weeks then I started having ZERO PSI on the freeway.
Me being ignorant I ignored the problem for a couple weeks as it still ran great.
I would get off the freeway and pressure would come right back up.
Then my injector pump blew up.
I should have switched pumps back immediately and it cost me.
DON't be a sucker, ignore the other comments in here.

THE PUMP IS THE PROBLEM. They simply aren't up to the task of WVO.
Damn I wish I had never taken this advice on this forum. There is nothing special about these pumps except that they are way too weak.
Sorry you were stupid enough to take whoever's advice on here too.
-120 $ on walbro pump
-330 $ rebuilt injector pump trashed
-70 $ for 24V humvee IP replacement
solution - go back to my old pump - a simple vane one (mustang high performance, high pressure one)
YES I RAN A looped return for over 6months on the old pump just fine. LOOPED return is not the problem. Although I quit looping my return recently, but im in TEXAS - there's just no point. I have plenty of heat and a massive racor 1000 to get it all hot before the IP.
The WALBRO pumps are crap. I'm sorry , it's the simple truth!