Testing the FSD? -Attn: GMCTD please!

[Cowracer]

Help Me GMCTD! You are my only hope.

Still no start on the big blue truck. :( In recap, the truck would not start after work on a bitterly cold day. It has not started or even given more than a half-hearted chug since then.

I have tried EVERYTHING upto and including an exorcisim. Fuel is quite good into the pump. Glow Plugs are new, cranking speed is fine (new batts and starter) and on and on...

The only thing left to replace is the FSD. Mine is remotely located in front of the driver's battery. I experienced stalling last summer, took it off to tighten the transistors, and relocated it to the heatsink. I have had no stalling problems since then. On inspection, the current FSD appears physically intact, no scorch marks/smells and the transistors are still tight.

I doubt its the FSD, as I dont see how a cold snap could kill it. But seeing how I am desperate, I am about ready to pop for a new FSD. If that cures the truck, I will pay the $300 with a smile on my face. But if the truck STILL dont start, I will probbly burn the POS to the ground in my driveway. :mad: :mad:

But before I spend the $$$, is there a way, with my trusty digital o-scope, to make sure that the old FSD is doing anything? Can you tell me what signals to expect on what pins on the FSD? What about ohming out the actual fuel solenoid.

I searched the forums, and I found some info, but not a definitive "YOU SHOULD HAVE A 7.2 VOLT 18Khz 50% DUTY CYCLE SQUARE WAVE ON PIN Z DURING CRANKING" kind of thing.

Any help is most appreciated
Tim

[DChristie]

Good Morning!
It'll take a couple of days to get there, but would you like to use one of my (known good) spares to test your truck and determine for certain if it is the FSD? I can mail/ship it to you post-haste.
Sorry, I don't know a thing about the signals coming out of the FSD or how to test 'em. I think it's PFM and voo-doodoo.


Donald T.

[Kennedy]

I doubt that moving a symptomatic FSD to a heat sink will help or cure it. Usually if it's breaking down it will continue to do so.

Buying a new FSD/PMD is not at all a bad idea as it is something you can always use...

[arrowheadracing]

Well I ll second the cold idea, up to the other day. Mine just took a dump and its been below 0 or slightly above for awhile. I had my original fsd still on the pump, plugged that in and worked like a charm. Check it out with a used one. And if you need a new one check out ebay or ssdieselsupply.com and talk to Walt. He carries them cheaper then most anbody I ve seen ( unless you score a good deal on ebay ).

Good Luck
Todd

[moondoggie]

Good Day!

As a former Electronics Tech., I

[gmctd]

Alright! I've always wanted to star in one of those 'only one man can save the world!' scenarios. ;)

As addendum to my response over in your carnivorous glow plug post, and assuming you could not pass the Limp Mode, Extended Crank test, and considering OPS and CPS each set a DTC at 8 missed pulses, compared to the other, if non-functional -

With non-intrusive signal test-point block installed between JK's ORIGINAL Beta test harness and Bill Heath's harness, 'bout 8ft over-all length, '98 engine idling -

A - Inject is PCM control - sharp leading\trailing edge pulse, about 8ms at idle
B - Drive is Fuel Solenoid Drive - sharp leading edge to +12v, ringing several cycles, holds 8ms to trailing edge, much ringing at 0v
E - Signal is FS pulse, triggered at FS Drive leading edge, drops after several excursions of leading edge ring, at ~1.88ms pulse width with 5288 IP, ~1.95ms with 5521 IP, with IP mechanically advanced +5deg for indicated +8.5deg and -1.5deg TDCO

Tech-II on '98 OBD-II, oem and Bill Heath re-flash, indicated -
690rpm
~1.95ms FS pulse width
8-10mm3 Fuel Rate
+7.5-8.5deg adv
-1.5deg TDC Offset
190deg ECT
70deg IAT
100deg Fuel Temp
60deg day, FSD\heatsink warm to touch, but not hot

'nother member was comparing similar trucks, one running, one not, indicated signals seemed identical, but never heard back from him.

Did not have defunct FSD on-site for comparison.

Also tested with JK-only 2ft harness, direct connected, for comparo - no change

[Cowracer]

DChristy~

HELL YES! If there is anyway you could have UPS/FED-X/USPS overnight one to me, it would help a TON.

When I return it, I will wrap it in enough cash to re-imburse you for the shipping charges, plus a nice box of Entamanns Chocolate Chip Cookies :D

Send to:
The Doe Run Co.
Attn: Tim Streisel
881 Main St.
Herculanum, MO 63048

Personal email addy is TPSTREISEL at yahoo.com

A thousand thanks.

Tonight, weather permitting, I will see if'n I get any signals like GMCTD indicated.

JK, I agree, buying a new one would not be a bad thing, and in the long run, I will. But I need to conserve my rapidly dwindling cash reserves until I zero in on the defect with my truck.

Thanks to all who replied.
Ya'all get me all choked up!

Tim

[Kennedy]

I think the key isn't heat so much once they are hurt, but temperature changes/extremes.

Typically once it begins stalling the end is near and it usually ends up DOA...

[Turbine Doc]

PFM & Voodoo is apt description of the FSD, one temp related thing, that will kill the engine is cold joint on pin sockets in the harness & at PMD interface.

If the female socket wells in the harness are loose, intermittent contact male to female with shut you down. Happened to me on R&D GMCTD was referencing, we had to back out pins and tweak them some for better contact, no problems since.

[DChristie]

Good morning!

Cowracer, did you get the FSD yesterday? and did it do you any good? (please say yes to both questions)It's no skin off my butt if you say no, however I'd much rather know the problem has been solved.
BTW, I like the red-eyes on da cow, would that be a Mad-Cowracer?

[Cowracer]

Don,

I was just about to email you...

The package came in yesterday, but the storeroom guy didn't bring it to me till this Morning :mad:

I'll try it out tonight. If it works, I'll get a new one tommorrow. If it doesn't work, then I don't know what to do next.

At any rate, I'll send yours back first part of next week.

Oh, yeah! The red eyes are for the Mad Cow. In fact, the license plates on my truck say MAD COW!

Thanks again
Tim

P.S. Is it just me, or does your FSD smell like Hoppes gun oil?

[DChristie]

Take your time, I won't need it anytime soon. :D And yes, it probably does smell like Hoppes gun oil. :rolleyes: I started keeping it in a gun case next to the .45. I figgered one way or another I'd be done with my truck. If that little black electronic horse-pill didn't work, then the hand-held Hi-speed drill would! :eek: Just the threat seems to keep the old goat in line. I hope it goes well for ya!!

Stay warm
Don