6.5 surging, black smoke

[joshsiller]

Friend of mine has a 98 K2500 with a 6.5 and a automatic. I has been surging quite bad, but mostly at lower throttle postitions. It is hard to start out on gravel without it surging and breaking loose. It idles smooth but it puts out black smoke under acceleration. It also surges the same with the cruise on. Replaced the lift pump and it worked good for a week or so but its back to its old ways. I think it is the injection pump, any way I can test it to confirm that. Thanks

[Hubert]

Any codes the DS pump is pretty good about giving some if the pump is failing. How many miles? If none I'd recheck fuel supply issues. Could be air in fuel line, fuel quality, or similar. How about filter new with new lift pump?

[joshsiller]

the check engine light is not on. I dont have a scanner to check the codes but i will get a shop to check them. The filter was changed the same time as the lift pump. I just talked to the owner again and told him to clean all the battery connections and grounds really good. another thing, the black smoke is not consistent. it will smoke, then quit, then a few minutes later it will continue again. The tach also jumps around lots when it is surging. drops like 500 rpm. thanks for the reply.

[JohnC]

If it surges under cruise control I doubt if it's the injection pump. There are many tight checks for uncommanded changes in fuel delivery. More likely it's the supply of fuel to the injection pump. I'd check the filter, the quality of the fuel in the tank, tank pickup, tank venting, oil pressure switch...

[meckervogt]

Hi folks,
I just bought a 99 3500 with auto trans. approx 138k km on truck . Dealer claims the injection pump was changed 2 years ago at 125k km. It has just started this wild surging, and I mean wild. Normally at slower speeds but also experienced it at around 70 - 80 km/hr. There is such a rush of power and black smoke that you have to stand on the brakes to reign in the beast! at first it scared the tar out of me but now I know whats happening so I can control it. Just as I was coming home this eveining I had to slow down to about jogging speed because the construction crew ahead was pulling the signs for the night. Well it started to surge so bad for a good 4 or 5 seconds, full on power and black smoke, very embarassing! I had to keep a lot of pressure on the brake to keep it stopped, I was trying to figure out if I should shut it off or not and then all was well again except for a couple of burps the rest of the way. The engine light does not come on so I don't think that its generating a code?
One more thing, I cannot generate anywhere NEAR that kind of power by mashing the throttle all the way down as when it surges, its like its getting a shot of NOX. Any thought or advice would be great!

[Robyn]

Welcome to TDP :D:):D

This could be a PMD in its death throws

I have seen this before.

Does your rig have the PMD still mounted to the IP???

If your PMD is remote mounted I would try a fresh PMD is not I would do a remote mount and use a fresh DTECH PMD

Keep us posted

Robyn

[meckervogt]

Hi Robyn,
Thanks for the welcome and the advice.
The PMD is still on the IP. I did order a remote kit and Dtech driver from one of the advertisers here on TDP, PMD cables, so I should have that here early in the week. It takes a while for orders to get up to The Yukon Territory sometimes! Anyway I went to give the girls a ride to the dance tonight and the darn thing almost redlined IMMEDIATLY upon starting the engine. Shut it down, tried to sart it again, no luck, it would just crank and smoke. Now it had been sitting for a couple of hours already since I last drove it but I spoke to my brother a 6.2 owner and he told me to cool off the PMD with some water to see if it would start. So I piled a couple of ice cubes on the PMD, took the kids to the dance in the car, came back, started the truck. I don't know if I should risk the 100 mile trip to the dealer, cause I'm sure I can get them to put another pump and PMD on it under warranty. The in service date is 08/99 so I'm good until next August. I guess if the new Dtech arrives before next Friday when my appointment is at the dealership, I'll try that first and see what happens!

[Robyn]

The redline off the gitgo and then shutdown is a sure indicator of a failing PMD.

The usual PMD thing is the stalling and hard starting but what you describe does happen.

I had it happen to me once. I was testing a few Used PMD's
I plugged in one and it worked fine, the next one I plugged in and the thing did exactly what you said.

Be sure to get a resistor for your new PMD. #5 will work if you dont know whats in the old one.

The resistor fits in the plug port on the PMD before the cable plugs in.
The resistor has two little holes with connectors that fit over the pins. Also the resistor will only fit one way.

Getting the old one out of the PMD on the IP is a bitch with the PMD still down in the hole.

Just do your remote mount. Be sure to leave the little ground wire that goes to the top of the IP right where it is.

Getting the plug off the old PMD is a snap with a little wiggling and a small screwdriver to lift the clip on the plug.

Keep us posted

Robyn

[meckervogt]

Hi Robyn,
So my new DTech arrived today, unfortunately I did not order a resistor, so me thinks I have to tear off some of the surrounding bits to get at the resistor if in fact I can actually unplug the silly thing in the first place! Man that looks tight in there! Are there any articles on TDP with pics showing any short cuts or hints? I've been looking but so far no sucess. I have seen pics of the pump and PMD on a bench but removal tips would be great. I would rather do it the easy/right way instead of reinventing the wheel again! Or should I just buy one of the books for sale on the site here that would cover this project. I'm not a mechanic by any means but can tear stuff apart with the worst of them!

[Robyn]

There are few shortcuts to getting the beast out.

With the intake manifold off the engine and "THE PORTS COVERED"
you can reach into the PMD with a little wire "PICK" and work the resistor out of the plug bore.

There are two small holes in the resistor that allow it to be grasped and removed.

Without pulling the manifold its pretty much a NO GO.

Now if you pull the manifold and then MARK THE IP to the front cover, you can then loosen the IP bolts and rotate the IP enough that you can get the PMD off the Pump.

Once out you can reset the location of the IP to the marks and then replace the manifold.

Now with the Old PMD in your hands you can easily remove the resistor from it.

This is the reasonm that most of us just forget the OLD PMD and the resistor and get a new one.

I personally would order a new resistor and wait to get it and not tear the thing apart.


Good luck and keep us posted.

Robyn

[meckervogt]

Well, I took your advice and am going to order a new resistor, so I phoned the local GM dealer, (160kms away) to see if they had one or could get one quicker then I could. They don't seem to know what I'm talking about. I explained to them that it should fit into the PMD before the harness is plugged in, no luck. Is there a GM part number that you know of? I checked the reference page and only found a GM # for the PMD but not the resistor, does a new Stanadyne PMD come with a resistor or am I/we missing something?
Thanks.

[enormiss]

I ran mine without the resistor while I was troubleshooting.
Dash light will come on, but IIRC no harm done until you get a new one.

[MTTwister]

Take the PMD off the IP. Then just for kicks, check the nuts holding the transistors. Bet they're loose. Tighten finger tight, then additional 1/8 of a turn. You should then have a backup FSD, for real emergencies.

[Robyn]

SS Diesel has these listed on their web site in the products category page.

The GM shop will likely muck this up a bit. Call the guys at SS or one of the vendors here and they could mail it to you asap Im sure.

Robyn

[meckervogt]

so..... my brother dropped by to give me a hand to unplug the pmd and remote mount the new one. Still no resistor, but he had it all unplugged in about 2 minutes and we had the new one hooked up. Presto, it runs perfect! good power, no surging at all, just a hint of black smoke for a brief second under full acceleration. I put about a half hour on it idling, driving around town and on the highway, no glitches, nothing. Also no check engine light. I was expecting it to throw a code without the resistor. I'll order a #5 in the morning from Dtech and throw it in when it arrives. Is there any harm in running without a resistor?

[Robyn]

The ECM only monitors the resistor every so many startup cycles.

Once the com puter looks for the resistor and sees that its gone it will complain (SES LIGHT)

Wont hurt to run it but I would wait to get the resistor in before going too far.

If the ECM sees the resistor is gone it will default to a preset value and this will effect power and mileage.

Now that you know your "Baby" is off the critical list :) I would wait for the resistor.

I think yours is only the second or third PMD that I have seen do what yours did.

Most failures are a simple stall or fail to start hot issue.

Glad your making progress

Robyn

[meckervogt]

Hey thanks for all of the helpful advice! I'm still not sure which resistor the Stanadyne paper weight has in it since its still on the IP, but, I have a #5 on order and will install as soon as it gets here. I'm still going to my local GM dealer to see if they will give me a new Stanadyne to carry as a spare since the other on failed. I hope a 200 mile round trip without a resistor doesn't hurt the truck. Sounds like i won't though.
I'm still amazed at how quickly the unit failed and how it failed. THinking about it now I'm glad that sucker didn't surge on me in a heavy traffic stuation or worse waiting for a pedestrian , cause wow, when it hit it was scary powerful!

[JohnC]

As far as I know, the ECM never looks at the resistor unless the value stored in memory is somehow erased. It may go for years without a problem. Once it sees the resistor is missing it defaults to the lowest fuel map, so your power will be as if you had installed a #1 resistor. No big deal. Get the new resistor in there whenever you can.

[meckervogt]

Well, I put about 300 miles on the new PMD, so far so good! Drove into Whitehorse to see the GM dealer about getting a new one as a backup and of course they couldn't honor my 1 pm appointment, I guess appointment means different things to different people. Anyway its scheduled in for next Friday for them to diagnose the old PMD. One of the techs looked at the extension cable, and heatsink, PMD assy, and thought it looked pretty good. I stuck it in front of the drivers side battery right behind the headlight so it gets pretty good airflow. Also it was a pretty hot day at least for our standards around 26 C or around 80 F. I'm going to borrow my brothers infrared thermometer just to see what the temp difference is between the 2 PMD's since the old one is still mounted on the IP, I'm just curios.
Now if I can figure out why it almost stalls when you shift into reverse or sometimes when you shift back into drive. Not always but sometimes. It seems like it only does this when you try to give it just a touch of throttle. By the way this happened with the old PMD as well. No check engine light on either so I'm not sure if this is normal for a 99 3500 with an auto tranny, everthing is absolutly stock except for the PMD!
Thanks all!
Martin