Abrupt near-dead engine: '98 Diesel G3500 Van

Hi folks: I would be so grateful for any suggestions or thoughts anyone might give me on this one.

I bought a used '98 G3500 last week. It is in very nice condition, and ran VERY smoothly for the week so far (about 500 miles).

I took it to a service station/inspection station here in MD today, where they took forever (4 hours!) and told me I needed new steering and brakes, $1200. Okay, I figured I'd go and get a second opinion. I drove about 2 miles, and it started hesitating. I had an experience recently of an unfamiliar vehicle running out of fuel unexpectedly, and I happened to be passing a diesel gas station, so I immediately pulled in and put in 6 gallons, though the gage read about 1/8 tank (several ticks above empty).

Almost immediately, the car started lurching and nearly dying. The engine wouldn't respond to the accelerator: it wouldn't die, but it wouldn't break out of a low idle. I got stuck completely going up slight hills several times. There was almost no power. It never died, but it felt like it was going to at any moment. At one point I saw clouds of perhaps bluish smoke out the back, but I was distracted and am not sure how my livid anger and the tense situation might have colored my perceptions. I stopped it for a while in a parking lot about a mile from my home, convinced I was going to have to walk home, and discovered after quickly checking it over and not seeing any obvious problems, that once it had cooled (I assume that was the key thing), it ran with much more power for a minute or two, before it started fading again. That was enough to get me home in a couple hops.

I figure either 1) the folks at the service station sabotaged it (in MD the inspection stations are also service stations, which seems messed up to me: a perverse incentive. Also, I'd wanted to watch their work but they took so long I finally went to lunch, and then they did it. But, they seem like very nice folks), 2) the timing was a coincidence, &*!#@ happens, and it could be anything, or 3) the gas station was cross-fueled, and I filled up with gasoline (I did nearly do this at the gas station, caught myself at the last moment and switched pumps, so I'm very very certain I was at the diesel pump, but I have heard of this happening. What does a diesel engine running on gasoline behave like?).

I'm sorry for the great length here, I just wanted to get all the details in one place. Thanks so much for reading this far, and thanks in advance for any help. I will probably try to take the time to get more familiar with the engine in the next few days, so any hints about where to start looking for answers are welcome. The only other thing that happened in the meantime was that I replaced several bulbs, including some brake lights that I wasn't strictly certain were the right bulbs, and burned slightly brightly, but I really can't imagine that has any bearing.

Warmly, Keith

Reply to
Keith Winston
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Sounds like a fuel problem, probably a plugged fuel filter.

Reply to
Steve W.

Greetings,

There could be either of two problems going on here - one simple and one expensive. But first take your van to a local auto parts store and have them pull the error codes from the ECM and see what they are, if there are any.

The simple problem is that you may have picked up a bad batch of fuel (loaded with water or algea or both) and that has clogged your fuel filter and/or filled your fuel-water seperator which are combined into the same unit. Several things to mention here - always carry a new fuel filter and read in the owner's manual how to drain the fuel-water seperator. That should be the very first thing you do right away any time you suspect a fuel related issue. Also, ONLY get fuel from stations that do a lot of business with diesel. The fresher the fuel the better. Diesel that sits in the stations tanks for a long time (or from a station that has bypassed the inline filter on their diesel pump because they're too cheap to replace them regularly) will cause more problems than it's worth.

The second problem that you could be experiencing is a very common (and could be a very expensive) issue with the Fuel Solenoid Driver (FSD). I believe that this is your issue because you mention that the van ran better after it cooled, but ran bad once it heated up again. The FSD is the black box that controls the fuel injection pump and are notorious for failing because they are mounted directly to the side of the FI pump and generate a LOT of heat. If you are lucky and catch it quick, you can get away with only replacing the FSD before it also damages the optical sensor inside the pump which requires an entirely new pump (~$1800.00+). If all you need is a new FSD, then you can buy one with a new calibration resistor for around $250.00 and mount it on a device called an FSD Cooler (~$150.00) which will allow the heat it generates to be bled off into the air and not absorbed into the FI pump. All you need to do is disconnect the old FSD and leave it on the FI pump, and install the new FSD and FSD Cooler per the instructions using the stock wiring harness. It's a 45 minute job in a van if you are mechanically inclined.

Good luck - Jonathan

Reply to
Jonathan

Thanks Jonathan, I'll check this. I was thinking of draining all the fuel out of the tank, replacing the fuel filter, clearing the lines, etc. Maybe cleaning the tank: I intend to run biodiesel sometimes, so a clean tank might save me trouble down the line. I will also check out the water separator, maybe that's all it is.

I think I have a code reader, I'll see if I can get them off it, or have some other place do so.

Other than the "ran better cold" hint, is there any other way to figure out what's going on with the FSD?

I just got the shop manual, but I'm pretty ignorant of diesels, but I think I'm about to learn a lot!

Thanks again for your suggestions.

cheers, keith

J> Greetings,

Reply to
Keith Winston

Yeah, I thought that was a possibility too. I hope to try all that out tomorrow, I was at a funeral all day today.

Thanks for your thoughts.

cheers, keith

Reply to
Keith Winston

Boy you sure said a mouthful when you said you're about to learn a lot about diesels! The 6.5L TD was a good motor but only as long as the owner was educated about them. Don't bother draining the tank as a first effort - draw off a sample and have it looked at. Someone at a diesel shop should be able to let you know and it will save you time, effort and money if it doesn't need to be drained. Also, use a good quality diesel fuel treatment - something that has an algeacide and eliminates water. It will also help keep your injectors clean and lubricate the FI pump. The FI pump is literally the heart of this motor.

First off, when you get some time go to the site

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It is a great resource for information about all GM diesels, especially the

6.5L TD.

As for determining if if is the FSD, yes I would drain the fuel-water seperator and change the filter (it's all the same unit). Like I said, keep a new filter with you and change it at the first sign of any fuel related issue. Injectors are not cheap, and bad fuel is too easy to get if you're not careful (BTW, this advice is applicable to all diesels, not just GM's).

If nothing changes, get the codes pulled from the ECM. There are two specific codes that tell you if your FSD and/or optical sensor are fried although I'll have to go back and research just exactly which ones they are. The post-'97 diesels weren't as bad as the earlier ones for eating FI pumps, but the FSD was always an issue in the factory mounting position. Rule of thumb was to expect an FSD replacement every 75-100k miles, and if you kept it mounted to the pump expect to replace the pump at 150k miles. The heat from the FSD not only fries the optical sensor inside the pump, but also thins the fuel which decreases its lubricity and accelerates internal wear - this is why I so fervently recommend the FSD Cooler to ALL 6.5L TD owners. If you are lucky you can get away with just a new FSD and cooler and still be OK. Search on the net for "FSD Cooler" and you will find more information than I can give you here. Installation is a snap (or at lease it was on my pick-up).

Don't bother trying to remove the old FSD if you think it's bad. That requires removing the intake manifold (bad enough in a pick-up, worse in a van) so it's better to just install a new FSD on a cooler and leave the old one in place.

As far as determining if it's an FSD issue, the "runs better when cold" clue is a biggie. Also look for power loss and eventually stalling when hot, and an increase in smoking (much less common) as well as the ECM codes. If your FI pump is about to head south and the ECM knows this, a clue to pick up on is that your cruise control won't work (the ECM disables the cruise at the first hard sign of any FI pump or electronic throttle issue). Honestly, if it was a fuel filter issue only then drive quality wouldn't be affected by temperature, but since your issue is temp related then the FSD is the Number One Suspect.

Here's another tip - don't have the dealer do the work if you need to replace the FI pump. Find a Stanadyne authorized facility that does their own remanufacturing and have them do it. The dealer (or any other shop that doesn't remanufacture their own pumps) will only send out to the Stanadyne place for a new pump and up-charge you for it, so cut out the middle man and save a few hundred bucks (more than enough money to pay for the FSD cooler which you should have installed if you need to change the pump). Besides, a dedicated diesel shop would have more experience than a dealer that may only sell and service a few a year, especially since you have the older diesel and not a newer Duramax.

Good luck - Jonathan

Reply to
Jonathan

I discovered some new things as I crawled around under my van today (I"m brand new to it, and to big, diesel trucks): I have a second battery, bolted to the frame just under and behind the drivers door! Is that normal? I think it's for an after-market alarm system. Does that sound right? I don't see any mention of it in my shop manual (I'm trying to get up to speed on this thing).

Also, there's a small cylindrical metal can in the fuel line, between the tank and the fuel pump, with two wires going into it: I believe it is the fuel lift pump. Yes?

Finally: a few days after I bought the van, I had trouble turning the ignition on. I put some graphite in there. The problem still happens occasionally. Somewhere in there, the key-in-the-ignition-like buzzer started going off whenever I opened the door, even if the key wasn't in the ignition (though it could be trying to tell me the headlights are on, or a door is open, or something else, I suppose). Anyway, I'm guessing the graphite is shorting out a switch inside the lock cylinder. Any other ideas are welcome. Thanks for any thoughts or ideas!

Warmly, Keith

Reply to
Keith Winston

Nope, Factory position for the dual battery option on the G vans. Notice the lack of room under the hood? They put the battery underneath because of that. You might also notice that your ABS control unit is mounted under there as well for the same reason.

Reply to
Steve W.

Kieth,

Due to the high compression of diesels (and especially the 6.5L TD at over

21:1) you need two batteries to provide enough cranking amps to turn the motor over to start it, hence the reason for two batteries.

The cylindrical metal can you see on the fuel line is the fuel lift pump and although I forgot I should have mentioned it earlier that you should have this checked out as well because a failing lift pump can also cause fuel related issues. Open the bleed valve on the filter and have someone turn the key to "run" without starting the truck. Fuel should flow freely out the bleeder (which will be quite messy so try rigging up a plastic hose to a cup first). If it doesn't then you have a failing lift pump.

If you have trouble turning the ignition key then try turning the steering wheel just slightly one way or the other as even a slight pressure from the steering wheel turned one way or the other could bind the ignition lock cylinder. As for the buzzer, there was a wire in the steering column that led to the Key-In switch in the ignition cylinder of my '95 Chevy C1500 that got pinched in the housing and grounded that would cause the exact same symptoms. I tried covering the wire with electrical tape for a while but ended up cutting it finally because it was just stretched too tight and I didn't need the Key-In buzzer anyway.

Cheers - Jonathan

Reply to
Jonathan

Well, I have discovered that there is no power to the fuel lift pump. I haven't figured out why, I can't figure out where/if there is a lift pump solenoid, I have heard conflicting reports on the 98 g3500 van, and I haven't seen it yet (my manual says there is one, but doesn't seem to indicate where it is). I wonder if it's been out a long time, the IP would have been working very hard, getting hotter, and prematurely age the FSD. That would explain why the FSD wasn't actually failing, but just increasingly heat sensitive. Maybe. I'm going to put in an FSD cooler, I would say.

Any help troubleshooting the lifter pump circuit is appreciated. Thanks!

Keith

Reply to
Keith Winston

Thanks Jonathan, I just posted my discovery that the fuel lift pump isn't getting any power. Thanks for your further observations. I forgot to add in my previous post: I have been assuming that the fuel pump solenoid in the engine compartment fuse box is for the IP, not the fuel lift pump. And that there's another solenoid out there somewhere. Since my manual is not completely clear on this point, I guess I'm going to try to find the relevant schematics and learn the system layouts for those two pumps: at least I'll have some clue as to what I'm looking for.

I discovered that the air filter housing was a little damaged, from someone not bothering to seat the hinge fingers before putting it back together: so the back may have been somewhat opened and unsealed for years. I got a K&N filter, and put it all together carefully, so at least there won't be any more air leaks (contamination) into the cylinders (and turbo!).

I finally got a look at the fsd, it's really buried in there. I'm going to try to take it off tonight or tomorrow, without removing the pump. That's my intention, anyway.

Thanks again for your help.

Keith

J> Kieth,

Reply to
Keith Winston

Yep, I did notice the ABS. So those two batteries are just mounted in a simple parallel arrangement I assume? Still 12V? I don't have the owners manual, just the shop manual, so I'm sure I could answer that question but I'm still digging through it trying to digest lift pumps and FSD's. Thanks for the response!

Keith

Reply to
Keith Winston

Keith,

Let's hit several topics here, in no particular order...

Testing the lift pump should be very straight forward. Just look at the directions for changing and priming the fuel filter - you need the lift pump to fill it after installing a new one. No lift pump = no fill. No fill = bad lift pump!

Problems with the lift pump could also be traced back to the issues you were/are having with the ignition switch, since power to the pump is triggered by the ignition switch in both the "Run" and "Start" positions of the key. Bad ignition switch = no power to the lift pump. Also check the ground on the lift pump because a dirty ground connection could also cause the pump to not work.

Yes, any increase in strain or workload for the fuel injection pump will generate more heat which will shorten the life of the FSD if it remains mounted to the side of it. Now get ready for the merry-go-round...

On the flip side, the FSD uses two high powered transistors to actuate the fuel solenoids. These transistors fire at four times engine RPM (or 8000 times per minute when cruising at 2000 RPM) and generate a lot of heat themselves. The idea was that this heat would be absorbed into the mass of the FI pump body and cooled by fuel flow that was either used by the engine or recirculated back to the fuel tank. This is the reason why many folks say never to run your fuel tank low if you leave your FSD mounted to the FI pump. On the flip side of that (yes, another side), this heat also helps keep your diesel fuel from gelling and forming ice crystals in very cold weather. Frankly I don't buy that last bit because it only applies when the motor is running and not after it's been sitting overnight in sub-zero temps. I think a good diesel fuel additive would work better than relying on the residual heat from the FSD. Yet another flip side is that the excessive heat from the FSD thins out your fuel which causes it to lose its lubricity and accelerates wear inside the FI pump as well as frying your pump's optical sensor. Lots of sides to this particular coin...

When checking the fuses and relays for the fuel injection, if you can't tell which one is for which pump then the one with the higher rated amperage (30 or 50 amps) is for the FI pump and the lower rated one is for the lift pump.

There is only one way to remove the old FSD from the FI pump without removing the intake manifold if you have the time and patience. (Note that this may not be possible in a van with the limited work area - I owned pick-ups that had the benefit of large, open work spaces.) Take a T-15 Torx driver bit and cut it so it's about 3/8" total length, then weld it at a 90 degree angle onto the tip of an extension bar. This is the only way to get the Torx bit into the bolts holding on the old FSD in the small space that exists between the surface of the FSD and the intake manifold. However, like I mentioned before if you believe your FSD is in trouble (there is no repairing one that is failing or has failed), just leave the original one in place and disconnect the wiring harness. Attach a new FSD with a #5 calibration resistor onto an FSD cooler and mount per the instructions. If you prefer (which may be a good idea in a van because of the tight space in the engine bay), you can purchase an extension harness and mount the FSD and Cooler several feet away from the FI pump and engine altogether. The best place would be somewhere that has good airflow like in front of the radiator or down low on the fender well away from the exhaust.

Yes, the batteries are in parallel - you need twice the amps to turn over the motor but it is still a 12 volt system.

Here's another item - if as you state below your FSD is becoming "heat sensative" then Yes, it is failing. These things cannot be rehabilitated or repaired, only replaced. Once they start to go they won't get any better no matter what you do to them. I sold my spare FSD on eBay when I sold my old truck, so I suggest you start by looking there for a new unit at a reasonable price.

Cheers - Jonathan

Reply to
Jonathan

correct, 12 volt, wired in parallel. Replace batteries in matched sets, never singles. Weaker battery constantly tries to charge its self from the stronger battery, resulting in no start at the worst possible time, and shortening the life of the newer battery. Remember O'Brien's Law one law, its easier, Murphy was an Optimist.

In the old days before sealed batteries, we would pull specific gravity readings and match batteries so there was no more than 20 points difference between cells. gets real fun on something like an M88A1 track vehicle recovery vehicle with 8 batteries.

Whitelightning

Reply to
Whitelightning

Hello Jonathan, thanks again for your help.

Yes, I think I've beat the lift pump issue to death. Apparently it was a bad (corroded) connection: after I dismantled every wire of the lift pump circuit (well, not quite but I did go so far as removing the Underhood fusebox), it just started working. I'm going to go back and clean all the contacts now.

That is another, and disconcerting, possibility. I also had a problem with the key-in buzzer going on whenever the door was open, and to solve that I snipped the light-green wire at the multi-function alarm. Who knows if that has other effects? I couldn't see any reason it would in the schematics. I didn't have any info on replacing the key-in switch (I don't think the shop manual covers it, though I wouldn't bet on it since it is so pitifully organized and indexed, like most shop manuals). Anyway, it looked like I was going to have to remove the steering wheel, which means the airbag, and I just decided enough's enough and snipped the wire.

I have ordered a cooler. I'll get a new FSD if necessary. I need to figure out where to mount it, people have said "under the fender" but I'm not sure I understand where they mean, since I wouldn't want too much road grime hitting it.

I'm going to play with this today, I hope. No kidding about the lack of space, though! Wow.

The dealer, apparently, washed out the inside with a power washer (no wonder it was so sparkly clean), so underneath the mats were soaking wet. I was concerned that the water wouldn't dry through the rubber mats, and would eventually rust the floor (never mind mess up the airbag controller). So I took everything out yesterday, seats, shelves etc, and removed the mats. The front mat was completely soaked, the rear was mostly wet around the edges. Now it just has to warm up here enough to dry them off! Meanwhile, my van looks very naked.

I've asked in another post, but maybe you know: can you use an OBDII scanner on this vehicle? I've gotten very knowledgeable-sounding people tell me both things. What I haven't had is anyone say "I had that van, and yes/no it worked/didn't." There is a distinction made in the OBDII requirements about "light" trucks, and this one doesn't qualify, and it appears to me that Chevy decided not to make it comply. But I'm not certain, yet.

Thanks again!

Keith

Reply to
Keith Winston

Thanks, that makes sense. I guess I'll just wait until I have problems, since the batteries seem strong for now. The top one looks newish, the bottom one looks older, so I guess I'll just wait it out. They would probably weather differently in those two positions anyway.

Keith

Reply to
Keith Winston

Keith,

Your van is OBD-II compiant. OBD-I ended in 1995 where there was a transition (and a lot of issues!), but OBD-II was fully in effect in 1996. However, if for some unknown (to me) reason your van is still OBD-I then you'll be able to tell right away the moment you try to attach an OBD-II code reader into the ALDL socket. If the OBD-II scanner cannot connect to the computer then there will be no doubt.

As for a mounting position for your FSD cooler, if you are also purchasing a harness extension then I suggest behind your grill in front of the radiator. Anywhere there is good airflow is acceptable just so long as you keep it away from anywhere mud can splash onto it and clog the cooling fins. I don't recommend inside the wheelwell, but mounting it on the wheelwell inside the engine bay (if you have the room) would work. On the firewall is just as good - airflow is the key.

Cheers - Jonathan

Reply to
Jonathan

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