New project 94 C3500 350

[tanman_2006]

Bought another headache...

94 C3500 Cab and Chassis 350 5 speed 100% base model, no AC only 2 speakers, manual vent actuators, and no cruise.

Got it for $1k. Has 105k miles on it, 6 new mud tires, and a clean interior. Runs fine cold, shifts good, and steers fair.

Once warm it runs rough, sputters and coughs, and can nearly die on you. PO said he tried 3 throttle bodies, all new plugs and wires, checked compression, checked fuel psi, installed a new intake manifold gasket, throttle cable, and a few other odds and ends.

My thoughts, cold advance or cap and rotor.

Goals: 3.42's, dash swap (for AC), thottle body and minor engine mods, and later on a 6.x swap if/when the 350 gets weak(er).

Purpose: tool hauler, parts getter, horse hauler in winter (working at sale barn), lml is for sale soon.

GMguy special:

 

[btfarm]

If that's still the old fashioned HEI distributor then I would suspect the pole piece insulation is cracking. Try a different distributor in that case.

 

[tanman_2006]

That's what I'm guessing too, cracked distributor. It drove home fine once up to speed. Occasional miss/stumble.

Running open manifolds will have to change soon though! Lol

I no longer have a timing light, any suggestions? I have a 93 454 to pick up too so I will have other uses too.

 

[tanman_2006]

I might need a refresher course on working I n a gasser. It's been 10 years since I had a TBI!

 

[GM Guy]

@tanman_2006 looking good! Its hard to stay out of the GMT400s, IMO once one has had a taste of perfection, its hard to move on. I need to hop one up so it can hang with the stock d-max and then I think I will have exactly what I desire in a pickup. I like the 06, but it doesnt have soul, the ol GMT400 made you feel pain when the temp guage creeps up, and it allways gets thanked for a job well done.

I need to snap some pics of dad's 92, I think it even has a J&I bed like that, they are basically twins!

His has a/c and the AM/FM radio, otherwise no other options.

I am experiencing similar issues with the rough running on his 92, improved when I replaced that little module on the dist, but still not great. If its running cool, it needs a t-stat for a proper ti

@btfarm do you recommend a GM/ Delco reman from the dealer? IIRC when I checked it was not terrible, I think under 150.

Also, what is the pole piece? is it the star wheel? if so, that is rust-jacking in this current one, has a little bulged up area.

 

[btfarm]

I used to buy an occasional rebuilt HEI but damned if I remember who sold them. They were good quality and 100 bucks with core exchange. The pole piece is a circular coil under the module mounting plate.

 

[tanman_2006]

My bed is hideous! Made me appreciate the bed on my 93 6.5 even more.

We are pulling the bed off my Duramax and setting on the 93 6.5, 93 6.5 bed goes to the 94 350. Dmax will sell bed less for now

 

[tanman_2006]

Tried paper clip, I only get 12 on repeat

 

[tanman_2006]

Interior pics

 

[ak diesel driver]

check out DUI (Davis Unified Ignition) they make HEI setups for a lot of different motors

 

[tanman_2006]

Custom fuel pump changing hole

 

[tanman_2006]

Do I need to pull the Distributor or just change the cap and rotor?

After thinking about it, he said he put in a new intake manifold gasket. That means he pulled the Distributor but when I asked him if he retimed it he said no. So now I'm wondering if he got the distributor back on correctly and if it's not seriously out of time.

My only issue is that it doesnt have a misfire code and I figured it would.

 

[Will L.]

If that was it you should have the code, but ive seen many strange things. Time to buy another timing light. Besides, if you want to time a db2 in the future, there are the opd mac kits (like mine) floating around that use a timing light instead of the "wear out" pickup coil.

Looks like the same guy in the military setting hmmwv procedures owned that flatbed.
http://www.hummerknowledgebase.com/fuel/ftac.html

 

[GM Guy]

remember to un-hook the tan wire with the black stripe (IIRC) when timing.

 

[tanman_2006]

Yup, tan with black stripe. I haven't found the plug but I'm looking. I've Heard it could be anywhere in the loom from glove box to the Distributor.

I talked to the local auto Mech school about getting them to check it out. The code thing confused me and we are planting wheat. They will work on it for cheap labor (like free) and I pay parts.

 

[tanman_2006]

Buying a timing light is on my list but not that high.

Looks like one burned plug wire bit doesn't look bad enough to hurt.

 

[THEFERMANATOR]

That engine does NOT use an HEI, or even a distributor REMOTELY close to an HEI. That is one of the MOST BASIC injection systems EVER built. It is DEAD simple. You have the distributor, pickup coil inside of it, no advance mechanism what so ever, igntion module to control firing for cranking, sending an RPM signal to the ECM, and then pass off timing control once RPM's go past roughly 275, then you have the TBI unit with injectors, IAC, and TPS, a MAP sensor, coolant temp sensor, a 1 wire O2 sensor, knock sensor, and 92 may still have an ESC that basically relays the knock sensor info to the ECM to retard timing, and lastly an EGR valve. There really isn't much to them. Most common problems with them are TBI gaskets, weak fuel pumps(stock fuel pressure is supposed to be 8-13, but TBI pumps are NOTORIOUS about not holding enough pressure to make the TBI injectors work well), injectors gumming up over time, and cracked pickup coils in the distributor. I've also seen quite a few of that style coils where they run good cold, but crap out when hot. There is NOTHING on that engine to set timing codes, it is up to you to make sure timing is set at 0 with the timing control wire unplugged(this basically cuts the ECM's control over timing, and forces it to run ENTIRELY off of the distributor and the ignition module). Also IF this engine still has an ESC(92 may or may not have one), they can cause all kinds of issues over time when they crap out. If it has one, it will be a control module mounted next to the solenoid for the EGR valve on the passenger side of the engine close to the throttle cable connections. You NEED a timing light to work on one of these engines though. It is MANDATORY so you can set base timing, and also to be able to monitor injector spray pattern.

But from what you're describing, I would suspect a bad coolant temp sensor, or a bad coil. It could also be base timing is off, and when it warms up the timing is retarding to far for it to run well, but you're going to have to dig in and diagnose it as throwing parts at these almost ALWAYS ends with somebody unloading them as piss poor parts creates more problems than they could EVER hope to fix.

 

[btfarm]

If that's still the old fashioned HEI distributor then I would suspect the pole piece insulation is cracking. Try a different distributor in that case.

As I said... IF that's... Apparently it isn't

 

[GM Guy]

Ferm, what do recommend for a Distributor in case Tanner (and I) need one? (brand/ source etc.) ours runs good cold, crappy hot, and drinks fuel. There is a star wheel riveted to a part in there, and it is cracked, so I assume this is the majority of the issue?

 

[tanman_2006]

Ok I took a 30 mile romp in the little beast today. Ran decent out of the drive but cut out bad at high rpm (no tach), once mid temps (I'd say 160-180ish) it was barely running, once it hit 190ish it smoothed out in mid range but no power down low and ran out of power by 75mph in 5th. It topped out.