How to tell if Injection Pump is going

[midnightrumbler]

I had a shop tell me that my Injection Pump needs to be rebuilt. Coming from the same shop that said I had no DTC's when my SES light was burnt out.

The problem with the truck is that I am getting a sort of jerking/bucking sensation around 60-100 km/h and gets worse when I put the cruise control on. The truck does not stall, it just feels as if there is lack of fuel which from the readings on my vac gauge this is not the case.

I have replaced the fuel tank not concerning this issue, redone some fuel lines, put in a new fuel filter and bled the lines. Before I purchased the truck a new OEM PMD was installed 1.5 months ago that has maybe 200 miles on it which was put back in the factory location. New air filter isntalled and I have cleaned up all grounds and checked my catalytic which is good.

I connected a pressure gauge to the WIF drain and I am seeing 6-7 psi at idle and 2-3 psi at hard acceleration. When the jerking sensation occurs, it does not effect the fuel pressure.

I have a turbomaster installed and I am getting 10lbs of boost. Other than that I am at a loss here. I do not want to toss $1200.00 for a new injection pump if I really do not need one.

I am not getting any DTC's at this time nor is the SES light on

Is it possible that the Optical Sensor is causing this issue? I am going to try and diconnect the filter and see if this helps.

The stumbling sensation is not always present when I take the truck for a test run. Just seems to come and go

The truck does over rev sometimes when I have had it out. say if I stomp on the throttle and let off, it will take a second or two after my foot is off the throttle for the rpm's to come down as if my foot were still on the pedal. I did get a dtc 25 about 2 weeks ago and have since cleared that code with no other dtc's being set to date including the dtc 25 setting resetting. Currently there are no codes stored.

Also, when I pop to oil fill cap off, I can hear a pinging sound coming from this location. Could this be an indication with the over reving and pinging sound that the armature could be broken? As I said, It does not happen all the time, just periodically. I have not had the truck out for a good long drive yet as it is still under construction and not on the road. I have been banging her on the back roads here getting up to 110 and keeping her in the 80-100 kmh range for some distances to see if there are any issues. This is when I am experiencing the bucking/stumbling issue.

I found a guy selling a rebuilt injector pump with FSD for $300.00. That sounds almost too good to be true but he states he has two of these and no longer has the trucks they were for.

I would hate to purchase a rebuilt injection pump and spend the time putting it in and have the same problems. Even at that, the FSD is worth just as much as the injection pump.

I guess I will try and relocate the 1.5 month old PMD to a cooler location and see if this helps at all.

Anyone in the Toronto area have a spare PMD/FSD I could try out?????

[Chevylover]

Did you run some fuel additives ?

Try to run about 1.5 quarts of 2-stroke-oil with each full tank (I assume you have a 34gal. tank, if not and yours is a 26gal. , than add 1 quart).

These IP's don't like the ultra low sulfur diesel (ULSD) actual sold at the pump. The IP, liftpump, injector need some lubricating. The 2-stroke-oil is made for burning, so there is no problem when adding to the diesel fuel.



Cu,
Sven

[midnightrumbler]

I have not run any additives in the tank as of yet.

I just received a DTC 36 - Injection Pulse Width Error (Time Long).

Would this indicate a faulty IP?

[JD_countryboy]

what kinda fuel you running, and how long has it been in tank? Has truck been sitting for long period of time? kinda sounds like your ip is gettin gummed up with gunk. What was reason behind changing tank? was it microbe growth in the tank? If so some if that stuff may have spread into your ip and has it gummed up. Try adding some diesel kleen additives and run thru it and see if this helps. Could even drain fuel filter housing, pull filetr and fil part way with diesel kleen and 2 stroke oil, put filter in, rebleed filter, start and run truck for a minor two and let sit overnight with taht concetrated stuff in ip, and see if it helps. Ive done this on old tractors that get gummed up from sittin for really long times without running. Exhaust will burn your eyes when you refire it, but if its your trouble, it will cure it.

[Chevylover]

I have not run any additives in the tank as of yet.

I just received a DTC 36 - Injection Pulse Width Error (Time Long).

Would this indicate a faulty IP?



Try what JD_Countryboy said and after that add 2-stroke-oil in a 1:200 ratio to every tank. That should cure the problem AND it shouldn't come back.


Cu,
Sven

[midnightrumbler]

I replaced the tank due to a crack in the upper portin of the tank. As soon as I filled it over half, the tank would leak.

I just purchased this truck and prior to me purchasing I was told it was sitting for 6 months. I have probobly put about 40 miles on the truck since owning it but all traces of old fuel have probobly been burnt off.

I am going to remove the filter management unit and clean it thoroughly as with 335,000km's, I am sure it has never been done. Who knows what is in the bottom of it.

I will also take your advise and run the cleaner directly in the filter managment with some 2 stroke to see if that helps.

I have been told there is also a little harnes about 6" in lenght leading directly into the IP that has a sort of pre-filter on it and alot of guys actually end up bypassing this as it can cause the issues I am having. Has anyone heard of that?

Will keep you posted.....

[Chevylover]

You mean the "Electronic Filter Harness 1994-1995 GM 6.5"

A failing filter harness can set codes 17 and 18. It can cause stalling after startup, hesitation and occasional 'fish byte' missfire ( one solid miss that commonly occurs at medium throttle).


Bypassing sound not good. leave it or get a new one, if you get the symptoms mentioned above.

Cu,
Sven

[JD_countryboy]

water in fuel will cause microbe growth. It will not simply just go away without treatment. Not garantein it, but if you do, you will also have to add some biocide to the fuel also, to kill and stop the microbe growth.

[midnightrumbler]

So i have removed the intake from the truck and noticed that the shop whom did the PMD has not replaced the lower intake gasket when they last removed it and I had several spots that were not visible with the intake on that were leaking. This is why I try and do all my own work.

Anyway, I also removed the fuel filter management unit and it had quite a bit of sediment (Rust, Debris et,) in the unit itself. The inlet appeared to have a small blockage in it which has now been removed.

Also, It appears as if someone else has removed this little rectangular piece under the intake that leads into the IP as I cannot locate the unit. Does anyone know what I am reffering to and should I put one back in place while the intake is removed?

That is about as far as I have gotten today. My next task is to remove the PMD from the stock location and remount it closer to the front bumper. I am going to splice and solder the connections and purchase the heat sink from my local parts store.

I will also get a new lower intake gasket and put it all back together to rule out my new findings.

If tghe above does not solve the issue, I will lean toward the IP. I don't want to rule any of the above out and just jump into an IP as this could be a very simple fix.

If anything, the engine will be cleaner as there was a huge pile of debris under the intake. Got to love shops, they are there to do the one task or multiple tasks they are assigned and do not even remove any debris or replace parts that should have been to lead to future problems. Freakin morons....Sorry in advance for anyone whom works at a shop but I have never seen too mnay good mechanics whom take the time or initiative to make things known.....
__________________

[roblo101]

Mine acked up hesitating go down the road, like you explained earlier. I purchased a new PMD and alum cooler that it mounts to ( with fins) same
wiring harness works an I left the old PMD where it was, just in case I have to hook it back up to limp home, (hope that never happens, ha!) This has been 3 yrs ago, no problem yet. Might won't to try that also.
What I like about this forum, we are able to read everyones advice and get a pretty dam good idea, I really enjoy this site,
Thanks all for your good advice
Rob

[midnightrumbler]

roblo101,

As put into a previous post, the PMD was replaced by the previous owner 1.5 months ago which is a stanadyne unit that maybe has 300 miles on it that was mounted back in it's stock location.

I have checked fuel pressure at idle and while driving, changed air filter and fuel filter, replaced fuel lines and remounted my PMD to the front bumper as well as relocated the OPS and installed a relay to the OPS.

I am still experiencing hiccups with my truck and have recently gotten codes 25 and 35.

I am going to try a different make of PMD to narrow things down and if that does not work, I may be into an IP.

I have been told it could also be the APP (Electronic Fuel Pedal Assembly) which is where the DTC-25 may be coming from.

Either way tossing money at could be's and would be's is a pain in the ass. Some say IP and some say PMD, most swear on the IP but it might as well be ABC's for all i care as I am pissing in the wind trying to diagnose this one.

I have owned gas vehicles all my life and diagnosing has been pretty easy, trying to diagnose a diesel, that is a different ballgame.....

One thing you are right about though, these forums are great to see problems people are experienceing and put comparrisons together. I appreciate your advise and will definately look into another PMD as I am thinking this could be it. Never know, the shop could have installed a used PMD and charged the guy $900.00 to put this in. We have all seen and heard that being done before. So a PMD I think has 300 miles on it could have 30,000 miles on it. If anything, atleast I will have a spare PMD/FSD