DTC 35 - Help!

[moondoggie]

Good Day!

I started this forum some time ago, & it got lost when the Page ISP goofed its backups. Since I might actually get to work on the truck this weekend, I thought I'd re-start the forum, in case anyone has something else I should look at. Unfortunately, lots of good posts got lost, but that's life. Here's what I started with last time, with a few additions to the list of to-do's I made as they came in:

**********

Well, I guess now I'm just one of the guys - I've got a SES light, with DTC 35 (per factory/Helms manual, "Injector Pulse Width Error (Response Time Short)"). This is on my '95 pickup. The truck starts & runs perfectly, cold or hot, although I haven't done a WOT when the SES is on; fuel economy seems unaffected. The SES comes on right after starting, then on & off while I drive.

I did a search in the 6.5L Turbo Diesel forum, searching by "DTC 35." I read all posts. It looks like I should (in approx. this order, due to a combination of ease of doing & likelihood of fixing the problem):

1. Clean connections at FSD
2. Re-torque FSD
3. Verify lift pump function
4. Replace fuel filter
5. Clean all ground connections
</font>

1. LH side by the headlight</font>
2. RH side by the headlight</font>
3. Under Dash (hidden by the ALDL by you left knee while seated)</font>
4. The main engine to chassis ground (I believe from the drivers side head to the cab)</font>
5. Both battery grounds</font>

6. Clean large harness on firewall, behind the injection pump
7. Clean connections at injection solenoid
8. Clean under Inj. Sol. cap? (ucdavis suggestion)
9. Degauss inj. Solenoid
10. Replace FSD
11. Replace injection pump

What else should I do?

One of the posts also said bad fuel could cause this, but not how this could be so. Any ideas?

My FSD is mounted to a home-made FSD cooler. My cooler is a 3/16" aluminum plate bolted to the intake (like the commercially-available units). I milled this to clear the FSD: the FSD attaches directly to a 3 1/8" x 4 3/4" heat sink, & the heat sink attaches to the plate; I used heat sink compound & NO thermal gasket. The FSD is on the bottom, the heat sink fins face up. There are 8 fins, 1" high x 4 3/4" (length of heat sink). (I am nominally an Electronics Tech., so hopefully I got this right.) I had moved my original FSD from the pump to this cooler some time ago. The FSD failed & was replaced 11 Oct 02. I intend to purchase an extension harness & move the FSD to a better location as soon as I can.

My story: We went camping, 4-6 July. I pulled our 20' camper ≈ 200 miles each way in 85 - 90

[BUZZ]

I wonder if a worn timing chain will set these 35 and 36 codes. Erronous type codes, I sometimes ge as well. I am running a FSD cooler with a 2 year old 20,000 mile IP. All grounds and related items function correctly. Engine does not start well since pump replacement. I wonder if slack timing chain is reponsible for poor cold starts.
Buzz

[moondoggie]

Good Day!

Timing chain causing DTC 35 and/or 36, or poor cold starts? I sure couldn't say, but it doesn't sound impossible. I can tell you that the ONLY symptoms I have are the SES light coming on, & loss of cruise control (which happens whenever SES is on, apparently). This truck starts & drives perfectly. In fact, it's quite noticeable how much better it cold starts than the 95 Sub.

Last weekend I cleaned up all the grounds I could find, so I'm in data-collecting mode now. The real fun (sick humor) of this kind of problem is you never know where it's going to lead you. I thought I had a definite IP problem; now I'm not so sure. I will not report any data until I'm pretty sure the data is solid; I will report any data as soon as it is solid.

Blessings!

Brian Johnson, #5044

[ 12-09-2003, 07:51 AM: Message edited by: moondoggie ]

[BUZZ]

The only symptom I have is SES and associated loss of cc. The cold start seems retarded. I only get a 35 or 36 on occassion, more so when the outside temp is in the 50's or lower. During the summer months no codes on cold start. After the truck is at full op temp in any weather condition, I get no SES. I am with you, I don't think the IP is the culprit.

[ucdavis]

re: cleaning behind fuel solenoid cap- this is not for the faint of heart. You are opening up the IP & must be clean-room picky about how you act with it open. I disassembled a dead IP & found piled up junk at the solenoid plunger that had to affect pulse timing; it looked like nylon plastic that had been ground up, along w/some fuel debris. I believe you can do this w/out affecting timing, but can't go any further cuz the fuel solenoid itself must be set for a tolerance-driven headspace to generate correct injection pressure.
re: dirty fuel, it was my speculation that junk could interfere w/the plunger to cause too long a pulse; perhaps too short is also possible from filth in IP.
Note about fixed pulse width: this is "back-up fuel mode" or limp mode. W/this you have lousy power on acceleration. If you have no power loss (you might not notice w/out a load) you don't have fixed pulse width.
Good luck, anxious to hear more.

[Uncle Wally]

On my 94 the ground strap from the body to engine and then the frame is on the passenger side head by the downpipe. The straps are no very long and seem to get dirty easily, so they are hard to recognise in low light conditions.

Waldo

[tom.mcinerney]

I recently checked all engine grounds on my '95. The one Wally mentioned--passenger head/frame/chassis(firewall) was the only one that was clearly "bad". The screw into the frame rail(near downpipe) was loose. This more likely to affect tail lights than engine....

[moondoggie]

Good Day!

Last weekend I did some of the list, so now I'm in data-collecting mode. I'll have something more here within 3 weeks or so. Thanks for all your input.

Blessings!

Brian Johnson, #5044

[ 12-09-2003, 07:51 AM: Message edited by: moondoggie ]

[moondoggie]

Good Day!

****************************** THANKS! ******************************

It

[David Brady]

Brian,
I would like to add my .02 as well after have DTC 36 get progressively worse over the last year and looking at a new IP. I replaced my intake manifold with a non EGR manifold and pulled and cleaned the bolts that handle the battery grounds as well as the ground in the back corner. This ground was tight on the bolt but not tight in the head and very oily. After clean up and installation my code dissapeared while driving. I have seen two lights which -I haven't checked, after the truck sits for 2 days apon startup for about 10 seconds and then disappears. So I think it is the ground at the intake in the back that had some kind of faulty connection as the others didn't seem that bad. I am very relieved as I did this work back at labor day and it still is working good. I wonder how many IPs get changed for bad grounds that are taken care of when the intake gets removed and cleaned and installed. Any how, I think you've got it this time.

[curmudge1]

FYI, FWIW, my story didn't work out quite so well: I had the DS4 injection pump fail in my 94 6.5TD Blazer about a year and 1/2 ago. I don't do major mechanical work, so I had a Chevy dealer, recommended by local Stanadyne distributor & who diagnosed the failed pump (after about 130-150K miles of life, iirc), install a refurb pump from Diesel Injection in TX (DP advertisers) -- after a couple months, it showed DTC 35s & set the SES (after running a bit at first, later almost right away after starting). Diesel Inj sent an advance replacement & I had it installed (different mech) & it started doing the SES & DTCs again after a month or so... I AGAIN checked the connections, but not the grounds. So, tried another dealer, busy GMC dealership... they installed a NEW pump & an updated chip for about $2200 (big OUCH), and Diesel Inj. took the pump back for a refund (GREAT SERVICE, I buy my SPF there, I recommend them). 'course I was out the labor $$ from the two prior installs, plus all the aggravation.

Both the Chevy & GMC Dealers said that they only install NEW pumps, no more rebuilds, because of problems. And, the Stanadyne dealers don't seem to be too savvy about the 6.5, they just know the pumps; Diesel Inj. rep said they just checked my returned pumps & sold to someone else & they report no problems (arggh).

I do recall one tidbit from somewhere that said that the 94s were more picky about the injection pulse width -- maybe that was why the GMC dealer replaced the chip? Anyway, it's been fine, no problems since (knock on wood). And I'm glad someone else got their problem fixed with just cleaning up electrical connections. Maybe my problem was the ground connections? And/or the chip? Are there any posted pictures of these ground connections, to help me find them?

[ucdavis]

NP Moon, That's why we're here.
So here's a thought for the checklist:
Lotta folks say OK, I'll clean the grounds; where are the grounds?
Why not obviate the search & start the ground quality process w/new grounds to dash, head2frame, etc for any that you can't find? All the checlist would need is a list of the ground strap locations & if you don't find one conveniently, cut a piece of #8 wire, put some suitable ends on it, choose a bolt (maybe choose the end locations B4 cutting wire), clean up & tighten the connections. No more fumbling to find stuff that might have been removed by some previous owner or tech.

[Uncle Wally]

Moon,

My 94 manuals say:
1 ground - pass side head to frame and body (this is a braided non insulated wire right by the downpipe.
1 ground - passenger side battery to body
1 ground - wireing harness to dash right above ALDL
1 ground - under bed drivers side rear near bumper

Since the manual is somewhat difficult to decipher, I'm sure I have missed some. But these are all on my 94. The one by the turbo downpipe is what I suspect are most peoples problems as the A/C canister has ice on it when used, it drips down on the frame connection when it melts. When exposed to the heat of the exhaust, corrosion rates increase. Mine were/are bad. I installed one from the front of the drivers side head to the frame and from the rear of the head to the cab.

Waldo

[moondoggie]

Good Day!

JDave: Great tip. Makes you wonder if curmudge1

[Marty Lau]

bumped to the top. [img]smile.gif[/img]

[moondoggie]

Good Day!

Update: It

[Uncle Wally]

Brian,

Glad you've had luck (knocks on wood) figuring out your problems. Hopefully I will be back to making clouds at stoplights soon!

Merry X-Mas

Waldo

[BUZZ]

Hi,
Since an IP replacement almost 2 years ago my burb does not start like it used to. Also started to get 35 and 36 mostly in the cold months. Even when plugged up did not start great. However since SES would go out once warmed up and truck runs great I have not been overly concerned. I did start to get a no start and shut down and so bought the PMD cooler kit. This solved the no start and shut down, but did nothing for the 35 and 36. Took a trip recently and SES kept me from using cruise. I started to get hacked off and determined to fix this thing. Orderd Helms books for $120. I don't have the books yet but last night I went out and checked all top side grounds. Founnd 2 suspicious ones. The braided one under trans dip stick bracket and a singel 12 gage or so that bolts to intake manifold passenger side rear, has heat shrink around it. I also cleared the codes. Well this morning at 22 deg F I fired up and guess what?

This thing has not started this good in 2 years and no SES light. So far so good.

Check those grounds is all I can say.
Buzz

[moondoggie]

Good Day!

It's as good to hear of this working for someone else (you) as it was when it worked for me. Well, almost as good.

I hope this solves your problem permanently, as it appears it has mine.

Blessings!

Brian Johnson, #5044

[Barry Nave]

Wally
I have all grounds as you lested though I have only one from pass head to frame and can't fine any to firewall.
Eng was R&R under warrenty 4yrs ago @ 65K for oil useage. By chance Mec. did not reinstall or may have not had one at the time?
Just do not see any ground at all to firewall.