Anybody having problems with optical sensors in the Chevy 6.5L injection pump? I have gone through three now. Seems to be something in my fuel. Girl Mark has given me some pointers to look for with fuel quality, but do these engines and injection pumps work well with BD? I own a '95 and '98 and have not had a lot of luck with them on BD so far. I think it was my last batch of brew, to much water in the final product made the fuel cloudy - it fogged up the optical sensor - then you have to replace it. If these sensors get grease like smuges it seems to be all over for them. I am thinking of a Duramax now.
Do not run cloudy fuel! This goes for any engine. Do not run unwashed in the 6.5 TD. These pumps are sensitive enough to other stuff, you don't need to be adding to their problems. The Duramax is approved for B5 only, anything else will void the warranty. (not that we care much about warranties on this forum) HTH.
Run cloudy fuel all you want in the old mbz!
My '97 6.5 is super finicky tho- must have
perfect fuel or it complains. I have had numerous
IP related problems but have not resorted to
replace more than PMD's (now remoted in front bumper)
Advise you change filter, remove all fuel, refresh with known good, clear #2 or biod,
and be super careful to take samples off
the petcock every 100 miles or sooner.
If you have a "dead" IP or bits, could I pay
you postage for them? I'd like to look inside
And I doubt your IP's died- they just got indigestion.
Palo Alto, CA
1997 GMC K2500 Suburban 4x4 6.5L td
1983 mbz 300D turbo
The IP itself was not replaced, just the optical sensor. I did drain all biodiesel, change the fuel filter and replace with #2. Still same issue. WHen the optical sensor was changed out all was better. $358 for the little guy, plus labor! But it sounds like good biodiesel works with these IP's then?
good fuel== good running.
Did you keep the part? I'd try just cleaning it
I've seen the optical sensor on ebay for about
Errr.. so whats an 'optical sencer' !?....newbie as only had my 6.5 td for bout 6mths..so far ok on washed bio...
Gi'day all, I started making BD last summer so I guess it wasn't the best stuff and it went to a 95 silverado 6.5L for the first "trials". Ran great for a while, then the optical sensor caught on and I replaced the injector pump twice. Before the pumps were replaced, the fuel system was drained and put back on dino but the engine would still randomly stall out, usually while accelerating form a stop. After this episode I shifted focus to older mechanical ip engines. A short time later as I had given up bd and the 6.5 was on dino fuel the engine gave out completely, flooding one cylinder with coolant. I think this has little to do with the bd and more with the hard life this truck has had, at this point about 190 thou km. The engine was replaced and I managed to get an ip warrentied so with better fuel this spring, I'm thinking about trying again.
Any wisdom on why the somewhat random stalling is this an automatic shut down from the optical eye? is it because the eye is still dirty from the previous fuel. If so how would you go about cleaning it.
A new puzzle I've got is with a four cylinder ford on our main loader tractor, it has run about 2000L bd in a 50/50 blend all winter a couple weeks ago it started to loose power gradually over a period of days till you could barely keep it running. Changed the filters(they had been changed once before not too long after bd conversion) this didn't help at all. Then we checked all the lines through the entire fuel system, no problems anywhere. Then we installed an electric boost pump and that helped a lot but it's still not 100%. This is a rated 105hp engine and it's behaving like it's 70hp or so. What I'm thinking is the seals might be going inside the ip, it's a mechanical and we've never had a problem before in about 5000 hours. What are the usual symptoms of a failing injector pump? and or anything better if you can help.
That stalling out can be either the optical sensor, or the PMD acting up.
The optical sensor is just a "safety" device that cuts out the fuelpump if the engine is not running. Many just disable it, reasoning that diesel fuel does not burn that easy, so in the event of a crash it would take a quite large fire to ignite the diesel fuel.
If I had one of those breaking down on me, I'd probably hotwire it too.
Any links to info on disabling the optical sensor? I haven't converted yet, but from what I've read it could be a potential problem in the future (along with overheating PMD's) so i'd like to familiarize myself with it.
Brian, do yourself a favor and replace your PMD with a remote one. I found myself stranded 200 miles from home because of a failed PMD. I have only myself to blame, because I was aware of the potential problem.
I haven't had a problem with the optical sensor 'yet'. I guess I shouldn't have said that .
No links, but here's how I would do it:
Just wire the fuel pump relay to a hot at igninition source and you'll be good.
For things like this I've found the GM-Diesel.com site very good. Hanging there a lot too...
OK, so what is the PMD? I have an 85 CUCV [blazer] I got from my uncle Sam, Some of you may have gotten things from him too, you know, there all green.
This is a J model 6.2 with a Manual IP but it does have a TPS on the side and a Diag plug under the dash so there must be a computer some where.
The book says it has a pre chamber in the head. Is this the same kind of pre chamber as in the Benz 300 and VeeWee TDI?
Do the Mill fuel lines and all that need replacing to run B100?
The 85s (J or otherwise)did not use a PMD. They were strictly mechanical (this is a good thing).
The TPS is for transmission control. Some of the military rigs used an oddball electric control for the 400 tranny. This they controlled with a TPS. If yours also has vacuum lines going into it that is also needed as the 400 has a vacumm modulator in the tranny. If the tranny shifts funny or not at all, check this TPS and then the vacuum pump.
The only way your engine would need a Diag port is if it used the 700r4. Doubtful in an 85 unless it was retrofitted. The TPS would be different with no vacuum lines.
Yes the 6.2 and the 6.5 share the same design of Ricaro swirl pre-chamber as the MB, though each engine design has a slightly different one depending on head design.
Being an 85 you should replace all the lines with Vitron or equivalent. I have found that normal lines only last about 6 months running bio.
Hope this helps
This is what happens when an old guy has way too much time on his hands. The bio-Buick now has lived for 18 months with a minimum of problems.This message has been edited. Last edited by: Shaun,
91 Buick Roadmaster wagon, GM 6.2 diesel conversion (gone but not forgotten
89 GMC 6.2 (Just got rid of the last pieces)
84 Mercedes 300D (gone to the great autobahn in the sky)
94 Cadillac Fleetwood (Sold before I could convert it)
I will look for the Vac lines. It sure looks like an OBD1 plug under the dash, I will pull the cover and have a look-see.
Where do I get Vitron line?
Also, What is this "Diesel Secret Energy" ? What scam are they running and why are they on the GM website?
But what does PMD stand foe and what does it do?
What about putting in an overdrive? Will the 6.2 take the added load of hi speed at 2100 RPM with the same millage? Or will the millage drop off a lot?
Lastly, anybody know where to get a flywheel for a manual trans? I have a 4 speed O/D with transfer case I would like to put in it?
PMD stands for pump mounted driver. It's also called an FSD (fuel solenoid driver). It is the electronic control box on the side of the injection pump on computer controlled 6.5L engines. Yours does not have one BTW. It controls fuel amount and timing. (The 6.5 is drive by wire). Non military 6.2s came with 700R4s and 4L60 transmissions. Basically the same. They were overdrive automatics. You can bolt one right in. Get a performance built one as they were pretty lousy transmissions. HTH.
So where do I get Vitron ?
I have the same problem with my 97 GMC 2500 4X4. I have been told by the dealer and the only other diesel mechanic in town that the IP has to be replaced. No one has just the OS and if they did, don’t know how to replace it.
I don’t think it’s a good idea to hotwire the fuel pump relay. It needs to be off when there is no need for it to be pumping. Like when the ignition is on and the engine is off. I don’t know if the pump or fuel line can take the pressure that will build up in situations like this.
Anyway, I’m interested in what fix you did and how it is working…
Doesn't hurt anything. When a Tech 2 is hooked up to the vehicle, you can command the lift pump on and it will run continuously. HTH
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