1994 6.5T hard start - Diesel Bombers
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Hey guys, new here but I own two 6.5T. A 94 1 ton and a 95. 3/4 ton 4x4. Recently the IP went out on the 94, installed a new pump, took it to a dealer to have the timing checked. Now you have to ... JOIN NOW TO REMOVE TRACER

1994 6.5T hard start

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Old 12-28-2010, 10:18 PM
Mrjohndeere's Avatar

Default 1994 6.5T hard start

Hey guys, new here but I own two 6.5T. A 94 1 ton and a 95. 3/4 ton 4x4. Recently the IP went out on the 94, installed a new pump, took it to a dealer to have the timing checked. Now you have to crank excessively and even give it a little throttle for it to fire.

Now, I've turned this site upside down..all the main ideas have been tried..

-new pump
-new lift pump
-new injectors
-optic eye
-clear hose out of pump...no air
-new glow plugs

Now it starts fine after the initial start...soooo

Let's brainstorm guys...my little sis drives this one to college.

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Old 12-30-2010, 12:54 PM
Crazy's Avatar
Diesel Bomber


I see you put new infectors in what brand did you put in did you have them pop tested if not maybe you have bad injector leaking down over night

Also see you put new LP (lift pump) but did you do OPS (oil pressure) test if OPS fail LP won't work and if do have to replace OPS make sure you put in ACDelco

Also seeing that you put new IP in is PMD still on the pump is need get off the pump if it still good and put in the front bumper

See you put in new glow plugs ? here is how long does your glow plug relay stay for and did you check volts going into the relay and out and did you check for power at the glow plugs

My other ? is how good is the batteries and how old are they if more the 6 months old have them load tested you just may have bad batteries and it not letting truck crack faster enough on first start these need cranking power maybe your batteries are doing ssome draining over night then after you get it started batteries back up and that way it start easy

Hope this help you out and let us know what you do fine

---AutoMerged DoublePost---

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

Crazy's Sig:Traded for 94 F-350 turbo blow the motor up little red
1997 3500 Ext Cab 2 Wheel Drive 300,000 plus miles New Trans with up grades for towing Rebuild Rear end 4:11 with
new axles,new injectors, 4" Exhaust , 5" tip, PMD Moved to front Bumper TM 18psi boost,,new LP,boost,EGT and trans gauges and Max E Tork T-Series

Last edited by Crazy; 12-30-2010 at 12:57 PM. Reason: Automerged Doublepost
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Old 12-30-2010, 12:57 PM
Mrjohndeere's Avatar


Injectors were NIB from a gm dealer.

PMD is on the pump still but it's the upgraded unit and we're about to relocate it.

OPS checked out fine, acdelco pump

Glow plugs have power everywhere and stay on for the same amount of time as the 95.

Batteries are dual optima red tops

Mrjohndeere's Sig:1974 IH 200 series 3/4 4x4 454BB chevy
1999 Z28 Camaro 11sec DD stalled/Cammed/sprayed
1994 Chevy 1 Ton 6.5T straight piped, chipped
1995 GMC 3/4 Ton 6.5T stock
...Oh and 15 John Deere tractors ranging from 40-225HP
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Old 12-30-2010, 01:26 PM
Crazy's Avatar
Diesel Bomber


Other ? what is your hight at when you first start just wonder if ECT working for cold idle start should be between 750-950 depend on what temps are one way check that is to unplug it and it should go up to about 900 to 1100 and it mounted in the T-Stat housing
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Old 01-05-2011, 03:20 PM

Default Need to ask a question

If there is no fuel at the injectors, (and fuel filter has been changed and fuel is flowing at the filter vent and the drain in the front of the engine, does it mean the pump is weak or bad or are there other issues to check?
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Old 01-05-2011, 03:36 PM
Crazy's Avatar
Diesel Bomber


Welcome to DB

not trying sound like @ss let not high jack Mrjohndeere thread start new thread i will be more then glad to help
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Old 01-06-2011, 12:17 AM
Woody35's Avatar
Diesel Bomber
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unplug the ect and see how the truck starts. have you checked the gp controller to see if its to specs?

Woody35's Sig:1997 Chevy K1500 4X4 EC/SB L56 6.5TD/4L80E
KOJO Tune, GM-8 Turbo gated @ 15 psi, 2100 PSI Pop Pressure Bosch Injectors,
Bosch Duratherm Glowplugs, Steel Braided Oil Cooler Lines,Relocated D-Tech PMD,Tekonsha Voyager Brake Controller
Autometer Gauges, ARP Headstuds, K47 Air Box , Flowmaster Crossover & 4 Inch Diamond Eye Exhaust
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Old 03-29-2013, 09:45 PM


Originally Posted by Crazy View Post
Other ? what is your hight at when you first start just wonder if ECT working for cold idle start should be between 750-950 depend on what temps are one way check that is to unplug it and it should go up to about 900 to 1100 and it mounted in the T-Stat housing
Punctuation is good.
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Old 03-31-2013, 08:12 AM
Diesel Fan


OP, did you do the OPS mod? Have you checked the Lift Pump when the engine is cranking over?

You could hotwire the LP to prime the system and see if that helps at start up.

Rattler's Sig:94 2500 4x4 suburban 130k miles
4:10 diff
OPS mod
Pretty much bone stock
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