Hello everyone. Myself and 2 of my friends are experiencing the exact same problem after having the injection pump changed under warrantee at our local GM dealership. The problem is that it now takes an excessive amount of cranking before the engine will start. One of the trucks usually will sputter and die after the first cranking cycle and then start on the second. Even with the engines warm, we are lucky to see a clean start at about 5 seconds of cranking. All of the trucks started within 1 second at the most, even cold, before the pumps were changed. We have all been back to the dealer and voiced our concern but they say "It is within spec." and pretty much just want us to go away. The trucks also seem to have a bit less power. There has to be a fairly simple answer here. Any ideas?

It sound like possibly the pump is not correctly timed.

Any number of things, cranking speed, supply pressure, glow plugs, battery connections could be causing the starting problems. I'd start with glow plugs.

A just replaced pump that was starting correctly before I suspect timing myself.

Cranking speed is fine, glow plugs are good, all conections and batteries are good. Remember, all 3 trucks were fine before this dealership replaced the pump and PMD on the warantee. Fuel supply is also fine. I asked them to check the timing and they said "It is within spec." I pressed the timing issue with them and they don't want anything to do with it because they say that it is "within spec". Not only did I lose power, but I also lost fuel mileage! One of the other guys owns a repair shop in town here and has the Snap On scanner, so we are going to try and figure it out without the help of GM. Just wondered if anyone has any ideas as to where the timing is best. Thanks for all your help!

1st thing to is use timing function to chesk timing, should be 3.5 degrees avg actual when time desired goes to 0, the other function you are looking for is TDC offset, on a MT2500 this value is displayed incorrectly, a stock setting for -.25 to -.75 factory spec using a Tech 2 compliant tool, MT2500 will show probably in neighborhood of -4.8 offset. An advanced time of -1.94 to -1.76 using a tech 2 compliant tool will show on a MT2500 as -5.4 offset. Found this out over the past weekend, I don't know why Snap On has such an erro display or why it only displays only to single digit, I am still waiting for Snap On to get back to me on that explanation.

When plugged into the MT2500 record desired and actual time set at idle that is a good piece of info as well.

was this pump new, like straight from Stanadyne? A lot of dealerships get their pumps from authorized rebuilders, and lets just say, there are those out there that are liscensed and shouldn't be. I'm of the opinion that even Stanadynes Test As Recieved specifications are too lenient. 16lbs minimum cranking pressure? C'mon, 5lbs supply so the transfer pump only has to up that 11lbs to be considered passable? A good rebuild will make 30+, but to some shops out there, that means spending money on expensive blades/liners/springbands/regulator pistons etc. that they consider unneccessary since it passes spec. Sorry, I'm just venting here, I had another pump come from a guy who bought one from a shop that we know to do shoddy work, and they had the nerve to charge him 1800 bucks for a half-ass rebuild, really chaps me to see that happen to people.

Actual and Desired timing must be close together. To reset this is one procedure. TDC offset is the next procedure. The dealer will set this to -.25* to -.50*. The optimum timing is -1.50* to -1.94*. Double check to make sure the lift pump is operational as well. To change the timing unfortunately you need a bi-directional reader (Tech II).

If three trucks all are doing the same thing than I would question the competence of the diesel mechanic on the job. He probably did all three trucks.

Firefighter,

Update your signature for equipment you have, it will help us better diagnose the problem. OBDI TDC offset can only be set with a T2 compliant tool, Snap On scanner can be used for OBDII but does not give exact reading as T2 for same settings as I indicated above, if you can access a GM T2 or Mac T2 that is easiest.

My friend with the shop has the Snap On scanner. I am not sure if anyone around here has the other types you mention. I do know that this GM dealership only has one guy doing the Diesels so I could probably be safe in saying he did all 3. The lift pumps are all working good and the pumps are new ones, not rebuilds. I am friends with the guy in their parts dept so he made sure we got new ones. I dunno. With the info you guys have given we are going to play around with the one truck on Saturday and hope to get some results. Thanks alot for all the help!

FF check your PMs I'm working Saturday also so will be able to take calls on the cell this weekend, I have my MT2500 with me so we can compare notes if need be.

Thanks guy's! I'll let you know what happens:D

I'm interested to know how you make out. I have the exact same situation, cold or warm. New IP from GM last june, truck started perfectly before, now its a chore. New glow plugs, filters, lift pump fine. My truck seems to have the same amount of power though.

Sorry guy's, didn't get to it this weekend. Had to tear apart a friends wounded 6.5. :( Have you ever seen a pison crack across the crown right above the wrist pin?-:t New one for me. All I can figure is with the cold weather we had and he had no block heater for a week or so and someone didn't let it warm up before they got on the loud pedal hard. :eek: At least it didn't do anything but loose compression. Very minor scuffing in the bore and that's it. Either way, it's not good. Anyway, I'll let you know when we do get around to trying the optical sensor bump.

I replaced the #6 piston 6,000 miles back. It had cracked across the crown. The truck has run fine since.

Ok guy's. Is the piece that the optical sensor mounts suppose to move? My friend got bored this morning and decided to try to bump the timing of the optical sensor but he could not get the lock screw to break free. He said that everything was stationary when he started and then all of the sudden the whole optical sensor and what it is mounted to was moveable after he had been trying to break the lock screw free. Now, here is where it gets interesting. His truck now starts like a charm:confused: Is this movement for the timing advance like a distributer has on a gas motor? He said that there was definately no movement when he started and then after cranking on the ratchit quite hard, there is movement. Did he break something or just break something that was stuck loose?

Hard to say. That T40 is torqued tight, it should be retorqued tight or it could move.

Where is this T40? He tells me that the whole assy that the opticle sensor is mounted to moves quite freely back and forth.

It sounds more like he was moving the cam ring back and forth with the optical attached firmly. It is attached by a single T40 torx bolt that has to be loosened to adjust it or remove it.

If it ran better from doing that it may indicate the stepper was not at full function (binding?).

QM is right, what he's talking about moving freely is the cam ring rotating inside the pump, which is supposed to be pretty free. You have to loosen the Torx40 bolt to slide the optic sensor under the lock plate to change the optic sensor setting... If the advance piston or cam ring were actually siezed in place for some reason, you would have timing/stepper motor codes, hard starting and either white smoke (retarded) or excessive clatter (advanced)

This might interest you to know, I just thought of this, a couple months ago we bought a pair of new DS4 pumps from a dealership that installed them and the did not operate properly, no specifics. Put them both on the test stand and the optic sensor was actually set improperly, but both of them were exactly the same. Got me kind of worried, I mean these were 'new' from Stanadyne, their sealing laquer still on the bolts, I was concerned that there might be something wrong with our test bench, so I rechecked the test stand, injectors, lines, graduates but found nothing wrong. Reset the optics to spec and sold them, haven't heard a peep since....

What I'm saying is that Stanadyne does make mistakes, and possibly the optic sensor bump could correct your problem, hard to say for sure without pulling the pump and putting it on a test bench, can you see the line scribed on the cam ring? It should be just visible on the pass side of the optic sensor, if there is a gap, then move the optic sensor to align the side with the scribe mark and try that.

I am going to get him to read your reply's cause that makes sense to me. Thanks alot for all the help. He did try to loosen the T40 and with a 3/8's ratchet on there he tried untill he thought he was in danger of snapping something but could not get it to break loose!:eek: He is cheif mechanic for an airline here, so I am confident that he was turning it the right way. LOL! He did say that the sealing laquer was still on the fasteners too. It would make sense to me then that Stynadyne must have set a whole whack of these optical sensors in the wrong position seeing as all 3 of us are having the exact same symptoms after having the I/P replaced under warrantee. What should we do to get that T40 loose? Have you ever heard of that before? I think I am going to tear into mine this weekend and see. Thanks again everyone!

The t-40 on mine was evil tight I was afraid I was going to break the IP off, but it finally came loose without damage. You said the power was up after messing around in there. The whole assembly in there floats a little side to side, I would suspect that when it settles back into its normal position your power will be back to where it was before, if you don't get that t-40 loose.

210in/lbs is the torque, there is a fat square o-ring between the bolt and the lock plate too, I've taken I don't know how many off, and never broken a bit or a bolt.

That floating assembly you mentioned MDT, moves constantly while driving, just pushing it to one side won't affect anything, as soon as the truck starts its going to move the cam ring to whatever position the PCM wants.