Hi all,

This will be a long post: I'm trying to solve several issues to at least get my vehicle and family back home to Lubbock, TX. Maybe someone has ideas. After two days of fixes and thinking I had things solved, I'm realizing I've made a big mistake in carrying on another three hours today. Forgive the long post. Perhaps my misfortune will at least entertain.

Summary questions:

1.
Can one burn out a Walbro pump with hot veggie? Mine (11psi frb 5) seems to be delivering much less pressure and fuel then it did at the start of the trip and in test drives. I'm afraid my looped return has fried the pump. But I'm still keeping 60mph on freeway when on the veggie side -- pressure just measures much lower than before.

2. So, I'd be happy to just run the diesel side, but my 7psi walbro on diesel will not allow freeway driving --- pressure drops to zero with throttle and engine bogs down. Some knock/rattle that suggests air leaks. New filter. I stopped at a NAPA and bought a carter pump as a temp fix and plumbed it BEFORE the walbro, but pressure still reads low with both pumps. Tomorrow I will see if the engine seems to run at freeway speeds. Should I try plumbing the carter AFTER the 7PSI walbro?

3. How do I know if I've killed my ip?

Now for the details on the system and the drama:

We have internet service at my hotel so I thought I'd see if any veggie and/or GM 6.2 gurus out there have ideas.

My wife and I and our dogs were trying to drive out to her folks in Arizona in our 1986 suburban 4x4 for thanksgiving. I have been building the truck for the last six months an we thought it was tested out. Drove it several hours from home last week as a trial. The engine runs great.

Here is the system: Stock tank for diesel, 70 gallon vegetable oil tank with hotfox and HOH to engine bay. Two electric fuel pumps (Walbro 7PSI on the diesel side and Walbro nominal 11PSI on the veggie).

The pumps are controlled by switch and relays. Veggie side goes to pump, then a permacool style filter with heater wrap, then a FPHE then through 1 way check valve to IP. Diesel side goes through stock filter then through check valve to IP. Nice thing is that there is no unheated veggie to IP. A Hydraforce valve does return to stock tank on diesel and loops to just before walbro frb5 veggie lift pump for veggie.

Veggie temps (sender right before IP) are 175F on the freeway.

We lost alternator and PS belts near Roswell and I bought extras and find I need to retighten after about 3 hours of driving (these are the high quality goodyears). That sucks but needs to be solved later. Alternator tested out at checkers. Of course with electric pumps not I need that alternator to drive even during the day! The other problem is fuel pressure.

Prior to this trip, I'd end up with about 5 PSI at idle on diesel (measured after check valves right before IP). THis would drop to 1 PSI or less on open throttle. On veggie side it was always solid between 5 and 7psi at IP. But that has dropped to 1-2 PSI over today. I stopped in Socorro and bought a carter electric pump to try to get the diesel side working strong enough to get us home 7 hours, but pressure now reads even lower even lower at idle (2psi) maybe the sender is bad, I hope?.


We had some knock/detonation noise that sounded like air leaks, not bad, but not how my nice rebuilt long block should sound. Nothing at idle and not noticeable at highway speed. SO I tightened hose clamps (including the one at the ip inlet that was loose) and it improved for a while.

Pulling into Soccoro the rattle was back.

So, my hope is to get enough fuel to the IP to make it home, probably tightening v belts every hour. My biggest fear is the ip is shot. I noticed diesel on the ground under the engine after I parked at the days inn. I can't check anything until daylight.

If we can get it running and feel safe enough to make the 3 hours of nothing back to Roswell we will abandon thanksgiving and head home. If I have to leave the truck in Roswell I can at least get back to it sometime.

Oh, and I love New Mexico. I just need to get home. I won't mention that many stupid tricks I accomplished on this trip like leaving my extra junkyard IP at home on accident.

Happy thanksgiving!

I hope things will work out for you.
Is the IP a Stanadyne DB? If so, there is a lot of info on the www.ford-trucks.com pre-powerstroke (pre-97)forum, as we have Stanadyne DB-2's.
I recall that fuel in the valley pan between the cylinder heads is possibly from a leaking/worn out IP.
Is there a way to disconnect and block off the fuel line somewhere before the IP to see if the fuel psi increases? This might tell you at least that your fuel pump is working.
Could there be a kink or restriction or obstruction somewhere in the line or fuel filter? You might try disconnecting the fuel line and see how much pumps out.
I remember being in Socorro last January (month 8 of a 10 month 21,000 mile veggie road trip) looking at 100 gals of great oil at the Arby's, but it was too cold for my 12v transfer pump.
Good luck,
Mike

quote:

1.
Can one burn out a Walbro pump with hot veggie? Mine (11psi frb 5) seems to be delivering much less pressure and fuel then it did at the start of the trip and in test drives. I'm afraid my looped return has fried the pump. But I'm still keeping 60mph on freeway when on the veggie side -- pressure just measures much lower than before.

2. So, I'd be happy to just run the diesel side, but my 7psi walbro on diesel will not allow freeway driving --- pressure drops to zero with throttle and engine bogs down. Some knock/rattle that suggests air leaks. New filter. I stopped at a NAPA and bought a carter pump as a temp fix and plumbed it BEFORE the walbro, but pressure still reads low with both pumps. Tomorrow I will see if the engine seems to run at freeway speeds. Should I try plumbing the carter AFTER the 7PSI walbro?

3. How do I know if I've killed my ip?

1. Maybe you can, depending on how hot the veggie gets etc. The old ones have given good results, but weren't engineered for SVO, so if one fails, greasers can't really complain too loudly.

2. I can't help thinking that your probs running diesel are more related to a pump that can't make adequate flow volume, rather than not being able to make adequate pressure.

You see, flow volume and pressure are linked. Even if your lift pump makes 1000 PSI, if it can't make adequate volume then all the extra pressure in useless.

The best way to reverse engineer what sized lift pump to use is to determine the engines' max fuel flow requirement at max load. Once you know that, find out what pressure your IP likes to drink fuel at, then buy a positive displacement pump that makes a little extra flow than required. You can then plumb in a bypass regulator that can safely bypass all uneeded volume and pressure until your engine needs more fuel.

3. Your engine won't start.

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

quote:

Originally posted by rkpatt:
I am very sorry to hear about your troubles .

I think that you are on the right track going back to the Carter pump ( stock pump ?) and getting the system back to stock to eliminate one variable. Make sure that you are getting a strong stream of fuel out to the IP . I also would recommend that you plug the WVO input side just to eliminate the variable of failure with the check valve and 3 way valve . Any signs of cross contamination (eg diesel odor in WVO )in either tank or unusual fuel level changes ?



Look around and post at the 6.2 forums at - www.dieselplace.com


More good Stanadyne DB2 stuff (Ford but basically the same pumps used for the GM 6.2) help on the IDI forums here -

www.dieselstop.com

www.oilburners.net

http://www.intellidog.com/dieselmann/idi.htm

Thanks guys,

The truck starts great, but the diesel walbro can't keep up flow as I increase throttle and this shows up as reduced pressure at the ip (stanadyne DB2). And bogging on freeway. Now a similar thing has started to happen with the other walbro. But on the veggie side I could still maintain freeway speed coming into Socorro. And there is still 1-3 PSI on the guage.

I will close the line between the ip and the pressure sender to see if I can reach full psi on either pump. I am worried that the ip is flowing more fuel somehow than it should perhaps to ip return.

So I think my panic idea last night of adding a carter pump before the diesel walbro may be pointless if it doesn't increase flow. I can try the little carter on its own and see how that works. I can't hear it work next to the clicking walbro, anyway, I assume it is running since it is wired up to the same relay.

Today: I'll tighten belts and try to find source of diesel leak in valley -- I hope it is the hose barb at IP inlet and not ip itself.

I definitely have fuel flow to the ip.

I hope I can get something together and my ip holds to get us home. The belts issue is a pain but I have enough spares and will check often. If I can even get back to Roswell we could rent a truck to get us home with our stuff. But that is a lonely 3 hours drive over the mountain away.

I didn't sleep much and its almost light.

Pulaski:

The DB2 pump will produce enough draw to run without a lift pump. Not at full throttle but it will run and even at high speed, the engine will start to surge as it starves itself of fuel. My suggestion is to get the stock GM rail pump (about 90 bucks) from a dealer or parts store. For now, by-pass all the veggie lines and loose the check valve at the IP.

Energise the new pump and make sure all conections are tight and not leaking. Note here, I have often had a situation that the line didn't leak under pressure but when under vacuum, sucked air, so make sure your lines are good.

If you have fuel in the valley of the 6.2, usually it means that either you have a bad connection into the pump, one of the high pressure fittings is leaking or you have a leaky throttle shaft seal (common problem). From what you are saying I suspect either the intake line or the throttle seal. If it is the intake line, then you are probably sucking air causing your timing issues or if it the throttle seal, you have effectively dropped dome pressure to ambient causing the pump to advance. You will probably have to remove the intake (well worth the 1/2 hour) and do a careful check. Occasionally the o-ring for the trailling port snubber (cone going into the back of the pump) does go south but that is rare.

Certainly sounds to me that you are sucking air and it probably is not the IP. These pumps usually give you lots of warning before they die. More then likely it is a plumbing issue.

Hope this helps

Bill

Also for now, eliminate the looped return and go back to stock return . Again go back to stock configuration and troubleshoot from there .

I dont think your pump is toasted. The fact that the poor performance is in direct relation to the drop in fuel pressure leads me to believe that you are dealing with simple starvation Vs a dead or dieing pump. If the engine starts normal then your advance piston and metering valve are not hanging up, the 2 things that can cause those pumps to "die".
The cause of the starvation probably isnt the filters since you changed them, but could be anything down line, clear back to the tank. Since time is of the essence, a quick (non permanent) way to see is it is a clogged tank pickup etc. is to buy a plastic fuel can, put diesel in it and run a short hose to the engine compartment. Have your pump and the filter the only thing inline, This will provide the least amount of restriction and possibly get some air infiltration potential.
As for the return, if it was me even on diesel I would loop the return into the supply side of the pump after watching the return flow into a container to make sure it is a steady stream and isnt aerated. It will help the pump and give you the least amount of restriction. I will acknowledge thet there are those who disagree with a looped return on diesel, but i have driven over 200,000 miles on veggie and the corresponding small amounts on diesel with this configuration and a stanadyne pump.
The other comment I have is that I have seen alot of pumps die due to a FPHE directly before the injection pump without a filter to protect it. I know there are people out there who have no problems, but I have personally been at the test stand when many of these stanadynes were autopsied, and every one that had a FPHE right before the IP had shards of brass and other metals in them from the FPHE. I suspect that in the manufacturing of them there is residual.
I always like to see a filter after the FPHE, just an opinion drawn from observation.
Hope all works out for you. You will get through this and then you will have a good war story!
Good luck!

Well, I don't have a mech lift pump with me so I can't go back to stock. I wish I could. The diesel side does return to tank and that is working. I can't plumb the veggie lines back to tank unless I could find a source of fuel line on Thanksgiving

Thanks Greasel,

I recently replumbed my system to put the FPHE right by the ip since I was getting a bunch of cold fuel when I had the filter first and max temps were low. One the other hand, at least the FPHE was flushed with about 20 gal of veggie when it was before the filter. After this trip I'll try to put a small filter right before the ip. Or if I can buy something today I will.

I'll see what replumbing I can do with the materials I have. I think the walmart across the street will be open.

Thanks everyone for the support. Yes, my wife and I will have a good story. But I've been an idiot.

I'm appreciating my reliable if somewhat worn old mercedes right now.

Also plug/cap wherever the looped return feeds back into the (tee ?) IP input line .


Don't feel bad . I think that many of us have been there . You are very lucky to have a patient wife . Let her know it .

Dont be so hard on yourself, Your doing the best you can and your motives are good. Tuition is paid in many ways and if you learn something from this it was worth the price. Although I know we all wish that the tuition could be paid on a payment plan without such steep interest!

take a 19mm wrench and open up the Frb5 and take out the filter that is in there. They make 2, a 40 micron and a 140 micron. They close up very quickly with the 40. I spoke to Kevin at Walbro and so long as you have a filter after the pump you can run without it. Of course you will probably plug up the filter before the IP but that is easier to replace than the Walbro under the car. At least that whast happened to me. Hope it takes care of your problem.

Would you mind to meassure the voltage you get at your electric pumps ?

BMW Fan

http://www.crawldog.com/klausold/

quote:

and loops to just before walbro frb5 veggie lift pump for veggie.

So the veggie pump is "inside" the loop? That means it is pumping around in a circle, rather than sucking from the veg tank. It has two supplies feeding it's inlet - the veggie tank, and the IP/injector return. That means that it will pull from whichever has least resistance, which may be airleaks in the IP/Injector returnlines. This makes your return line under vacuum, and they are a highly likely source of bubbles. I've always put the veggie pump "before the loop", so it pressurizes the entire loop. Any leaks result in fuel leaking out somwhere (usually at one of the returnline connections), rather than sucking air in.

The lower pressure you're reading may be due to air bubbles sucked into the loop, and the pump is trying to push them (mixed with fuel) to the IP. This may also indicate something is creating a higher than expected resistance between the veggie tank and the loop/valve, such as clogged filter, or clogged screen (maybe the one inside the pump), or gelled goo in the tank.
Cheers,
JohnO

There's been debate about where you loop veggy back into the circuit. Your argument for pre-pump is valid but can be helped by restricting down the inlet with a needle valve to add resistance on the return, adjusting possibly to the point of making it almost neutral for vac / pressure - at which point you've restricted it too much. Better to keep it on the pressure side. Like maybe 1 psi so you know you're not "sucking the IP dry" / introducing air on that line.

Hi folks,

Well, we managed to rent a car from the guy who owns the local steakhouse to drive the 3.5 hours to Arizona and the inlaws. We had a Thanksgiving dinner that couldn't be beat and didn't get up until the next morning when we headed back . . .
to the truck in Socorro this evening.
Because I was able to make a detour through Alburquerque I bought a GM electric pump for a 6.5 diesel as was recommended. I knew I should really do more diagnosis before doing this, but this was friday and the last chance to get it. Well now I know it does not seem to be a problem with the specific pump.

We did some more diagnosis but need to continue in the morning.

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.

If I crimp the fuel return while the engine is off with the pump running, the psi is higher than uncrimped.

It really seems to me that I have some sort of internal leak in ip with the ip letting too much diesel to the return.

Basically, the problem is that I am getting lower and lower pressure over time since leaving Lubbock on either diesel side OR veggie. ONly the veggie side was looped (to the inlet as the pump), and the veggie side has better pressure. Veggie was 5-7 psi running down the freeway but I stopped in this town because that too was now down to 2 PSI. I have not tried the veggie side since stopping in town.

My concern was that the veggie side would end up with as little pressure as the diesel side. ONly the ip is common between the two which makes me suspect that rather than simultaneous clogging of both systems

So I understand the debate about where to loop return, but right now I'm just trying to get the diesel side to work which is currently return to tank. I may try looping the diesel return to pump outlet to get enough pressure to get home if that helps.

I will check the voltage at the pumps and I hope that explains everything if there is a bad lead or ground that developed! I should have done that already -- I had to go buy a voltmeter. Perhaps a relay or connection is bad. First thing in the morning.

Oh, and my wife is awesome. She is actually the one who pushed for a 80s diesel suburban because she hates newer cars so she doesn't blame me too much. She has her 79 mercedes and likes old trucks but nothing past about 1990.

You are talking about alternator / belt problems.
That would make your voltage drop because you solely depend on your batteries.
Lower voltage….less fuel supply ……

BMW Fan

It does, indeed, sound like your IP is passing too much fuel to the return, but let's think about what else might cause similar symptoms (and hope to hear from someone who's intimately familiar with your truck's IP). Despite the reputation for weak IP's that GM engines have, this sounds bizarre for an IP failure.

Your test results that indicate reduced pressure with the engine off and fuel pump(s) running either indicate unusually low-restriction flow through the IP, assuming the pumps are working normally, or normal flow restrictions but with reduced flow from the pump(s).

As BMW mentioned, low voltage to the pumps might result in low flow rates, with reduced pressure at any particular flow except when deadheaded. Checking voltages might help diagnose that, but it might be instructive to observe the flow rate as the pumps fill a bottle. You might discover that they just aren't pumping much liquid, or you'll prove they're working just fine.

If the pumps had internal clogs, such as a screen as mentioned above, or just sticking parts, then they could also have reduced pumping pressures due to internal leakage (I've experienced this with a couple different pumps). A flow test would show this problem.

Here's a mildly dangerous diagnostic method: loop a fuel line up to where it can be seen while driving and watch for bubbles. This can't be simulated with a parked vehicle because the fuel flow rate isn't the same as when driving.

You've got a couple check-valves in your fuel system. Might they be clogged, or leaking air?

Might there be something wrong with the hydraforce valve? It's common to both fuel systems, too.

Does the IP return line also connect to anything else that could be bypassing the pump or valves? Most systems I've worked on (not GM) have the return line Teed into the injector returns, and sometimes a filter bleed.

This is a much more intersting problem to read about than to experience first-hand. You've got my full sympathy. You're also lucky to have an understanding wife.

I'll keep an eye on this thread during the day, but I really hope your next posting will be a report of success.

Cheers,
JohnO

Could it be a plugged fuel pickup screen in the tank?? open when its has low start and idle flow,then closes as fuel flow increases.
what about the return check valve on top of pump? i have gotten home by just drilling the center out of it, timing changes but a tempy fix!
Thx Ron