I have a 95 3500 LLY and need some help.

I am not a mechinic, but have a basic comprehension of tools and the workings of diesel engines.

PROBLEMS

1) the truck sputters

When you floor it it hesitates, like its running out of gas. Sometimes it does it sometimes it doesnt. Its really frustrating.

2) Its hard to start

If its cold, I turn the key "wait to start" light goes off and it almost starts, and then dies out...I try to start it again, and pump the gas pedal and it starts, and blows a huge plume of white smoke. The smoke goes away a few seconds after start up, but it engulfs the neighbors house on start up.

3) The truck is slow

I know its a heavy truck, but it has the pickup of a moped. People flip me off when im going up hills. I can floor it, and it doesnt really go faster...it just eventually gets up to speed.

4) Bad mileage

I am lucky to get 12 MPG...I dont know if thats good.....

Repairs I have Done

I replaced the OPS, the lift pump and a few other little things. I have a K&N in the stock box, and brand new injectors and lines and a new turbo back exhaust. None of which helped the above problems.


I really need some help here. I use this truck as a work truck, and I am just about out of business as it is, but paying somone to help me will just about do me in. I have heard lots of things, like there is an optical sensor in the IP or that I should check the fuel sock on the tank. I just need some help....please.....

Any codes?

The OPS may have given up again. Do the LP and OPS test again?

Turbo wastegate solenoid may be out. This one usually trigger the SES.

Better yet, may want to DO the checklist for thorough diagnosis.

X2 fill out the check list. Is the waste gate working and is it still vacuum controled?

Actually I just forgot to mention that....I already replaced the wastegate solenoid, and did the lift pump test...it passed.

OK here is the checklist....


1. Does the engine crank, or 'turn over'? yes
1a. Does the engine start and run? yes
1a1. If the engine does not start - Crack injector line (http://www.dieselplace.com/forum/showthread.php?p=2188140#post2188140): do you have fuel? Yes/No
1b. Do you have a Wait To Start Light & the amount of time (seconds) lit.8 sec or so
1c. Ambient Condition (temperature outside indicate F or C) around 80f____ °
1d. Engine Cranking speed (if you have an accurate tachometer). dont know
1e. Are you experiencing stalling? yes
1f. If Stalling, describe (upon startup only, down the road, hit a bump etc)It never stalled until the other day, twice in the parking lot of a store.
1g. If Stalling, do you notice loss of dash or instruments?no
-note if experiencing stalling,you must indicate PMD location in #24.

1.1 Lift pump test (http://dieselplace.com/forum/showthread.php?t=39350)- describe results PASS
2. Service Engine Light while running?- on/off/intermittent. no
2a. Service Engine light does glow during start/cranking/bulb check: Yes/No yes
3. Model year 95
3a. Odometer reading (indicate if in miles or km) 186.000
3b. Miles on major engine components if been replaced (example Injection pump) not sure
3c. Indicate the model number on the Injection pump (starts DS4 or DB2......) not sure
4. Have you scanned for engine codes? (varies by pre/post 96) yes/no yes
5. List exact results on engine codes (http://www.dieselplace.com/forum/dtc.php): no codes shown
6. Air Filter condition (visual check) changed not long ago
7. Fuel filter condition (freshly changed/condition unknown/mileage since changed) new
8. Condition of Battery terminal connections (removed, cleaned and tightened) checked and cleaned
8a. Known condition and age of the batteries. good
8b. Are batteries of differing age or are they a matched set? pr
8c. Condition of Major Grounds (http://www.dieselplace.com/forum/showthread.php?t=157085). (same drill as batt - removed, cleaned, retightened) brand new starter
9. Upon cold start, does the radiator hose get hard quickly? Yes/no not sure
10. Upon cold start, do you have excessive white smoke? Yes/no YES
11. Do you have excessive cranking time before the engine starts? kinda
12. Have you used the block heater, and does this effect engine starting?(only try for starting problems) helps a little, but still hard
13. During hard acceleration, do you have excessive black smoke? Yes/no yes
14. Do you have any unusual exhaust smoke issues? lots of white smoke on start up.....black smoke under acceleration or hills
15. Turbo check out (http://dieselplace.com/forum/showthread.php?t=39368)- pass/fail I have a boost gauge, and on hills and hard acceleration it shows maybe 4 or 5.....almost never more than 5
16. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit) I dont know
17. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD. 3500
18. Indicate fuel that you are using: Bio-diesel, #2 Diesel, #1Diesel, SVO/WVO, other....I use the on-road diesel whatever that is
18a. If running a VO (Veggie Oil fuel) setup, indicate details of your conversion (homemade, or packaged system)..no
19. Are you using any fuel additives? If so, please list. no
20. Please indicate geographic region you are in: (example: Texas or Canada) new jersey
21. Do you have any service history available that might pertain to the problem you are having?new injectors, glows, wastegate solenoid, OPS, lift pump, fuel filter, air filter and exhaust.
22. Please indicate any modifications to the vehicle that might help us diagnose better. none
23. Upon unscrewing the fuel cap (http://dieselplace.com/forum/showthread.php?t=42338), do you have a large vacuum formed in the tank? yes/no no
24. Location of PMD/FSD (http://www.dieselplace.com/forum/showthread.php?t=39436)? On the pump/remoted over intake/remoted out of engine bay (please specify placement specifically) its on the side of the injector pump I think....it says stanadyne...I think its aftermarket
24a. If remote mounted, describe wiring harness (homemade or purchased from a vendor?) it was there when I bought it
24b. Indicate the location and condition of the FSD/IP grounding wire. not sure
25. Are ALL glow plugs in proper working order as per this thread (http://www.dieselplace.com/forum/showthread.php?t=39182)? new
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I would first try unplugging the coolant temp sensor located on the Tstat housing at the front of the engine. Two wire plug, sensor is brass. Do a cold start with that unplugged. That will advance the IP timing and fool the system into thinking it is rather cold out. Mine is having trouble on cold starts but with that unplugged, it fires right up. This should indicate a timing issue with the IP. No biggy to fix.


I also do not think your turbo is boosting right but some simple testing will show that. You either need to find someone with software for that truck to see if the truck boosts OR get an OBD1 diagnostic cable with either an RS232 or USB plug depending on what laptop you might find to use, and get the free ware version of GMTD. It will at least show the boost pressure so you can just go drive and see if you have boost at all.

If the vac system is not working, you should be seeing codes though. Never the less you can easily unplug the vac line from the vac pump to the WG solenoid and test for vacuum at idle right from the pump.

Discovering if the truck has boost or not will help a bunch. However, I have found these trucks drop boost on the highway right when they need it and is part of an ECM programming flaw. You may be time and hassle down to put on a spring on the WG or the "turbomaster" mod. Sucks that there is not a chip or ECM reflash available that will cure these programming issues (at least that I can find) so we have to take a cave man approach to WG control but it will work.

interesting.....I have never heard of that...I am going to try disconnecting that sensor tonight when I get home and I will report back....

I had a VW rabbit non-turbo diesel and I would say the truck drives like that...cant get out of its own way...........I have an 03 jetta TDI now and you can feel the turbo kick it, its actually a quick little car....

I also checked the vac system. When the truck is off I can move the wastegate arm freely, but once I start it, it is locked. I did check and am getting the right amount of vaccum in the lines.

Looking at the PMD still at original location on the side of the pump, it sounds like a PMD issue. Sputters, start, die and won't start, etc. The only way to test it is with a good working PMD.

There are a vendor that is highly recommended by members here which is Heath PMD Isolator.

Or it can be the pump also.

Somone told me that Stanadyne is an aftermarket PMD...is that true?

How much is one roughly, and is it hard to replace?

OK, I came home and unhooked that sensor that was suggested, and the truck started right up, no smoke at all.....I didnt test drive it though.....so what do I do now?

the temp sensor in the thermostat crossover i'm guessing? when you unplug that sensor it tricks the computer into thinking its -40*F outside so it gives you more glow time. the sensor could be bad(ohm it out to be sure).

You will want to test the resistance between the two pins of the sensor with a multimeter. The truck will need to be dead cold so over night is best and the ambient air temp needs to be known. If you post up the results, there is a guy here that looked it up for me to determine if it was within spec. I am guessing you are ok.


The things that should happen when you unplug is advanced injection timing for cold start, increased glow time (which I did not notice with my truck when unplugged), and a raised idle. I am really thinking you need to have that IP timing checked or set at this point. The timing for a cold start is critical I am finding out.

You may luck out though and the CTS is all your problem and it is relaying the wrong temp to the ECM. I wish mine would be that easy.

OK....I do have a multi meter.....so what do I do?

My local mechainic is a great guy, but admits he doesnt really know diesels...is there anyone near extremely north jersey.....almost orange county NY?

OK....I do have a multi meter.....so what do I do?

My local mechainic is a great guy, but admits he doesnt really know diesels...is there anyone near extremely north jersey.....almost orange county NY?
Hi dezil, Take your ohm meter and go from that sensor connector to ground.
do this when cold. your reading should be 1802 at 95 degrees F, 2238 at 86, 2796 at 77, 3520 at 68.... that should cover this time of year..
that will tell you if sensor is working properly.

I have a 95 3500 LLY and need some help.


What do you mean "LLY?"

this will sound stupid, but should it be running when I do this? There are two holes in the plug, which one do I do this with?

LLY is a Dually....

Okay, that's a bit better, I was thinking Duramax LLY for some reason.

this will sound stupid, but should it be running when I do this? There are two holes in the plug, which one do I do this with?


You will be testing the "two" pins inside the sensor. If you look inside the socket where you pulled the plug out of, you will or should see two pins in there. red to one pin, black to the other, meter set on ohms. Truck is not running for this.

ok its 78 degrees, and it measusred 425

If that is indeed 425 ohms, you just found a major problem. Keep in mind though, I said dead cold truck. If you still have heat in the cooling system, that is a problem. If it is not cold, check it in the morning and if it reads anything close to 425, get a new one and you hopefully found a problem there.

i bought a replacement CTS for my truck for about ~$15 at napa. i replaced it when i did the t-stats. might just replace it and see if it helps out.

That is probably GOOD advice given the circumstance...

OK, I will re test it tomorrow and see. It hasnt run since sunday morning except the 30 seconds today, and that was 5 or 6 hours ago....

If I remove the sensor, is there a gasket that needs to be replaced? Will coolant come out? Will I need to purge the air from the system?

That is probably GOOD advice given the circumstance...


if nothing else its cheap insurance. i'd say test the sensor one more time and test the new one if you get one. that way you'll be 100% sure if the sensor is bad.

OK, I think I made a dumb mistake here...last night when I tested it I was testing the plug, not the sensor, and that read in the 400 range. This morning I tested the sensor, and it ranged from 1400 to 1700. I would say the ambient temperature was 69 degrees this morning. So what does that mean?:(

OK, I think I made a dumb mistake here...last night when I tested it I was testing the plug, not the sensor, and that read in the 400 range. This morning I tested the sensor, and it ranged from 1400 to 1700. I would say the ambient temperature was 69 degrees this morning. So what does that mean?:(


if its in the appropriate range then that would mean the sensor is ok. disconnecting it advances the timing, gives longer glow duration, and a high idle so it will start easier. when its turning over normally(CTS sensor plugged in) do you get white smoke? i'm wondering if maybe you've got a gp or two out or not glowing totally(just tip or just center) under normal glow time and the extended glow time when the CTS was unplugged the plugs had a long glow time so any worn out ones could have heated up fully in that extended time. just a thought.

Yes, with the sensor plugged in, I have a hard time starting, and a lot of white smoke....A LOT....when I unplugged the sensor, it started immediatly, and no smoke. According to the post by another member, the resistance seems low....about half of what it should be, so I am going to NAPA at lunchtime and getting a new one. Am I going to get covered in coolant when I take the sensor out? Will I need to pruge the air from the system?

I had all brand new AC delco glows put in just a few months ago....:mad:

I think just buying a new sensor and trying it is a wise move with the bit of confusion in testing methods. As Dave said, simply testing the new one compared to your old one at the same temps should show if the old on is bad.


I am not convinced the glows are a problem though. IP timing is similar to ignition timing in a gasser and critical for a good start. Injecting too late can cause poor starting. Yes, you will have coolant coming out of the hole where the sensor comes out. Just have the new one ready and get your finger over it. Should not loose too much coolant over the deal.

I agree...I went on my lunchbreak and got it.....a whole $19 isnt gonna break me, even in this crappy economy. I tested the new unit with my ohm meter and it shows 1800 instead of the 1400 the one in my truck shows.....my question is 400 ohms a big difference in resistance?

I am familiar with wrong ignition timing in a gasser, and I would say that this does seem to be very similiar. I will change out the sensor and report back.

OK, now im really frustrated.....I installed the new sensor, and there is no change....still is hard to start, and blows a ton of smoke on startup.....and if that wasnt bad enough, it leaks:mad:....I did teflon tape it, maybe I shouldnt have....

I test drove it and no change. I turned it off and waited a few hours, and unplugged it, and it fired right up with zero smoke, and ran great. So its not the sensor.....what do I do now?

As I said before, you should have your IP timing checked. This will require software and know how. As far as your new sensor, I will give it a bit more torque to see if it will dry up. They use pipe thread on those so they take some torque to get leak free sometimes.

I pretty much expected the sensor was fine but now you know for sure. Next step you can take is pull the glow plug fuse so you will get no glow time for a cold start, unplug the CTS, and fire it. My bet is it will still fire right up and you need to time the IP.

ok.....which one is the glow plug fuse?

I do have a laptop, and you said that the software is available as freeware....where do I get that cable you were talking about.....

will this work?

http://cgi.ebay.com/ebaymotors/GM-ALDL-Cable-w-OBD1-USB-Version_W0QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el 1247QQcategoryZ43989QQihZ001QQitemZ110036334944QQr dZ1QQsspagenameZWD1V

Yes, that cable will work for your OBD1 cable. The software I was referring to was just to check boost pressure. You will need to either buy software or have someone set the timing for you. I think in this circumstance, you should just find someone to do it since you will end up spending 300 bucks or so in cables and software.

Let me ask this....what would happen if I drove around with the sensor unplugged to see if thats really my problem?

that sensor controls the high idle as well as injection pump timing advance. i've also heard that that sensor won't allow the trans to shift into overdrive if it tells the computer everything is cold still. i've just heard about the last one, but I don't have the time to test it out myself to be sure. to kill your glow plugs pull the eng 1 fuse. that will also kill you fuel heater, WIF sensor, MAF(if "S" engine), the wastegate solenoid, and the EGR solenoid(if "S" engine). the eng 1 fuse shoudl be a pink colored wire(if you can see it) that runs ignition power to everything stated above. with that fuse removed you will have to crank and crank to get the truck to start, and you'll get white smoke from the exhaust because of no glow plugs. i've tried that myself and it matters what temp it is outside it seems. if its cool outside it takes a while to start(if its winter temps cold then it won't start), but if its hot outside it fires in a few revolutions of the motor. again this is with the eng 1 fuse pulled so the glow plug controller does not get power.

try starting the engine cold, run it for 1-2 minutes then shut it down then open the rad cap, is there pressure in the system. after doing that run the engine and open the t valve at the front of the engine to see if fuel comes out. also look at your vin #. it is up on the dash near the windshield. is the 8th digit an "S" or an "F". have you run a vin check on this site yet. might tell you when the ip was last replaced. chances are the ip will last longer than your little black box on the side of the ip. that is why so many on this site remotely mount their fsd outside of the engine bay. the ip does a fantastic job of cooling it right up until you shut the truck off then heat soak from the ip kills it. Ed

How do I know if the little black box is bad, or the injector pump is bad?

The truck passed the lift pump test, does that help?

Also where is the radiator cap, I cant seem to find it.

How do I know if the little black box is bad, or the injector pump is bad?

The truck passed the lift pump test, does that help?

Also where is the radiator cap, I cant seem to find it.

The radiator cap is located atop the overflow tank, back by the firewall on the passenger side..

Whatever Ed said.

If everything is eliminated, then the favorite PMD may be the cause. Unfortunately, you have no way to know if the PMD is bad other than replacing it with a new one.
If you get one, make sure it is relocated outside the engine compartment. You can search here to see the different solution. The favorite is one made by Heath Diesel with 7 years warranty.

If PMD don't fix it, then it may be the IP.

What does the PMD do?

I see the PMD isolator that heath sells for $550....whats the difference between that and buying a new stanadyne PMD for $150 and relocating it in the bumper nostril?

the difference is that Heath's comes with a 7 year warranty and a track record of no failures.

I have probably started the truck with the sensor unplugged maybe 15 or 20 times now, and it starts right up immediatly every single time. I have been trying to find somone that has the software and know how to set my IP timing and cant find anyone. I live in northern NJ and I dont think there is anyone around here.

Any suggestions? Should I get a new PMD before or after I get the IP timing set?