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Old 08-03-2005, 07:29 AM   #1 (permalink)
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Reference Material: Hard Starting

So, you say you have hard starting?

Well, this is a common problem, for many of the years of diesels that GM had. However, the problems are altogether different. For pinning down exactly why you may be having a hard-start issue, you’ll first have to start with what type of engine and fuel system you are working with.

Now, before we get into the complexities of the fuel system, let’s eliminate something simple first. If you have a hard start condition when cold, it may be a simple glow plug issue. Check your glow plug system first before proceeding to make sure it is operational. Glow plug problems are most noticeable in cold weather conditions. You will usually get a lot of white smoke on startup. This usually indicates insufficient heat for ignition.

Now, if your glow plugs have passed the test, forge ahead into the pool of diesel.

There are two main types of “systems” we’ll call them. First is mechanical injection, and the other is electronic injection.

Mechanical injection is found in years up to 93
Electronic injection is found in years after 94

Maybe you are a little confused, and your application maybe a step van, or something other than the norm. How do you identify your type of fuel system? Check the model of the injection pump. You’ll see a number system such as this:


Now, there are various numbers that you will see, but basically you are looking at the first three letters. DB2 is mechanical, and DS4 is electronic. You can also be tipped off by the “PMD.” The PMD is the little black box that usually resides on the side of the injection pump. (Fondly referred to as the IP) So, a PMD will mean electronic, unless of course someone stuck one in for decoration. That’s not common though.. . ..

DB2’s are still out there, but they are getting fewer and fewer. DB2’s commonly have an issue with a no hot start issue. This usually occurs when you have a worn head and rotor within the injection pump. If you have a no hot start, do this simple test. Take about a pint of room temperature/warm water and slowly pour it over the injection pump. This will cool it down and you may be able to then start. Now, notice, this is not a GM “approved” test procedure, but it will show if your IP is to blame or not. Please also note, do not use COLD water, but a moderate amount of room temperature water. Too much may cause thermal shock and something further down the line to crack.

Can I fix my head and rotor? For the most part, no, you’re not going to be able to do this on your own. A fuel shop that works on these pumps will be about the only way you can go. Replacement of the injection pump may be another way of fixing this issue.

Now, the DS4 pumps have different no-starting issues. They rarely have the same hot start problem that a DB2 has, but it has happened. Some of the many issues that arise with them are caused with the PMD.

How do I troubleshoot and pin down if it’s a PMD or not? There is a whole thread devoted to the PMD and you can go there for more information on that. A PMD usually has an intermittent failure, as opposed to what you may find with a mechanical injection pump, that just won’t plain start. Not so say that a PMD would just outright die on you, but this seems to be a lesser found case.

Fuel supply issues. Make sure that you have a working lift pump and OPS. These two things will frustrate getting the engine started because the injection pump has more work to do.

Are there any other problems with the DS4 pump? Well, the nice thing is, the computer will usually tell on you and pop a code. Depending upon the code, you may get extended cranking time to get your engine started. If your Service Engine light (SES) is on, have your codes checked. Up to 95 is OBD-I style, and you can check it yourself with a paperclip. After that is ODB-II style, and you’ll need a code reader.

Cranking speed - A diesel must have good cranking speed for it to start. A slow turning engine will not get the heat built up, and the injection pump turning fast enough for it’s pumping needs.
My engine is not cranking fast enough. Where do I start? Well, several different contributing factors will slow down the speed. They are:

Battery cables - a known weak spot in the charging system. Poor contact, corroded cables and the side post setup are all causes for electrical woes.
Batteries - diesel engines are very hard on batteries. You have to rob about a hundred or so amps just for the glow plugs - then you really sting them with starter trying to turn a high compression engine. You may get 5 years out of your gas engine batteries, but don’t be surprised if you are changing your diesel batteries more often. If your batteries are in doubt, you can have them removed and tested.
Starter itself - if your starter is getting weak, it may not be turning up to full speed. Check all the above first, before deciding upon repairing or a new starter. Many have posted improved cranking speed from improved connections alone.

Maybe you’ve got a situation where you have a no-start condition. One of the things you can do, is check to see if you have fuel coming to the injectors themselves. This is the last part of the fuel system itself. Simply loosen the nut on the back of the injector and see if fuel squirts out while cranking. If you have no fuel there, you’ll have to back track and figure out why. Now, just because fuel because fuel maybe there, does not mean that there is enough pressure to “pop” the injector open, but fuel delivery to that point will help better understand what’s happening where.

Air leaks - in the fuel system too may not be helping matters any. Check around the fuel filter bowl and see if you have an oily residue under it, in the engine valley. If your filter is leaking, it may pass some air through the system. Filter bowls can be rebuilt inexpensively.

Fuel cap - this may not be the outright cause of a hard start issue, but it may not be helping either - especially if you have any type of air leakage in the fuel system. When you remove your fuel cap, you may hear a slight "hiss." But if you are hearing a long WWOOOSSHHH - time for a new cap. Make sure that it is a DIESEL cap. Gas caps will NOT work. Diesel caps are vented to prevent vacuum from building, although a very slight one will build.

There will be additions to this post as time goes on.

Maybe you don’t see anything here that would contribute to why your engine is not starting. Start by posting your findings from what you’ve gathered thus far. From there, we will be able to clue you in better possibly after providing more details about your truck. Remember to place that information in your signature line, because it helps all of us immensely to pin down your problems more effectively.

Look here-> GM 6.5 Reference Material & FAQ's <-Look here

Diagnostic Links & Common Failures: Turbo System * Lift Pump/OPS * PMD * Stalling

°Please include your vehicle details in your signature line. Did you read the FAQ's and search before posting?
*Bus 1, rest in peace. Bone stock, now just bones. 4.10 rear 10/13 mpg, 182,000 miles with a set of MCI motor coach seats.
*Currently driving an "Canadian Camo" Snow White 2001 5.7L Chevy Express.
*Bus 2, 99 7.3L PSD.
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Old 08-03-2005, 08:39 AM   #2 (permalink)
Matt C
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With my truck when I start it in the morning it lets out a big cloud of blueish white smoke and runs rough. I let it warm up for 10 min and get in to take off and it blows smoke and chugs when I put my foot in to it. Once it is warmed up it goes away. When I start it 4 hours later it does the same thing over again. GM replaced the IP under warranty. I had to put head gaskets in it so I also put in new injectors and glow plugs. But when I put the glow's in I used 60g's, I think this might be the problem. Also it doesn't crank over very fast. I am not sure if the smoke when taking off could be related to starting it 10 min before or not. Help Thanks.

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Old 08-18-2015, 03:33 AM   #3 (permalink)
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I'm new here, I'm trying to help a friend out with a 1995 2500 6.5L VIN F. I fuel going to the injector pump, but not to the injectors. I had to drain the fuel tank, fix a bad wire to the lift pump, install a fuel/water separator, and replace the batteries. I don't wanna jump to conclusions about the injector pump being bad, but I don't wanna assume the fsd is fried. Truck has been down for 6 months. Tested for bad connections. So far got voltage to the fsd, but wiring diagrams I've seen here and online seem to read differently. Truck cranks, but won't turn over. I just can't seem to get fuel to the injectors. Any ideas?
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Old 08-18-2015, 10:49 AM   #4 (permalink)
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Welcome to the Forum!

After installing the new fuel filter set up, did you bleed the air out of the system? You can jump the lift pump relay to save wear and tear on the starter:***...stalled.jpg%22

Any DTC Codes?

Try a known working PMD with a resistor installed. Best is to remote mount it on a heat sink. Look up angelofishes on Ebay for parts to do this.

Full set of 1995 C/K Truck factory manuals here:
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Old 08-18-2015, 12:48 PM   #5 (permalink)
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Also go through ALL Grounds..... Connections must be clean,tight and no corrosion or frayed wires
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Last edited by OkDually; 08-18-2015 at 12:49 PM.
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Old 08-18-2015, 03:58 PM   #6 (permalink)
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Thanks for the info guys. I don't have an extra fsd on hand. I'm a heavy diesel tech. I'm used to Cat, yanmar, john deere, onan, isuzu. I'm new to small trucks like this. Truck looks like it's be jerry-rigged a lot. Tons of spliced wires everywhere. I've gone through the wires up to the fsd. Solenoid works, just can't get system bled past the pump to the injectors. Strong crank. The dealership diagrams are really difficult to read for me. I pulled the return lines and they seemed to be feeding fine. I just don't wanna tell someone they need to buy a $300 part and it doesn't turn over. Do the dealership manuals have instructions for reading codes? The part stores around here told me to use a paper clip and just count the service light flashes. Really appreciate the help guys.
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Old 08-18-2015, 06:19 PM   #7 (permalink)
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Here are the OBDI codes with instructions how to read with a paperclip:
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