No start

[Pappy G]

I am at my wits end on this truck. 98 GMC Sierra 4wd. 350, 4 speed. Yes we converted it from auto to 4 speed....
Truck was running fine, then died. Cranked and acted like it wanted to start but coughed and sputtered. Zero fuel pressure at rail. Ran diagnostics, new fuel pump installed. Good pressure at rail. Still no start, same cough and sputter. Changed crank sensor. Started up and purred like a kitten for about ten minutes. Then it started pinging and dieseling and finally quit. Now I am back to no start like before. still have good fuel pressure.
I am at the point where I am ready to remove everything electronic and go old school with an intake and carb on it with small electric fuel pump.

 

[Schurkey]

98 GMC Sierra 4wd. 350, 4 speed

I bet the 4-speed conversion was no fun at all. The computer tuning is entirely beyond my skill set.

Truck was running fine, then died. Cranked and acted like it wanted to start but coughed and sputtered. Zero fuel pressure at rail. Ran diagnostics, new fuel pump installed. Good pressure at rail. Still no start, same cough and sputter. Changed crank sensor. Started up and purred like a kitten for about ten minutes. Then it started pinging and dieseling and finally quit. Now I am back to no start like before. still have good fuel pressure.

Connect a scan tool, look for "codes" but more important--look at the data stream. Verify each sensor's output key on-engine off, and then key on--cranking. (You can't verify O2 sensor until it's warmed-up and engine running.)

Do you have spark? Is the initial timing correct?

How old is the distributor cap, rotor, plug wires, and spark plugs? The distributor itself is a high-failure item; in particular the gear at the bottom, the bushings the shaft rides on, and the distributor cap mount screw-holes.

You say you have fuel pressure at the rail. Do the injectors actually spray?

I am at the point where I am ready to remove everything electronic and go old school with an intake and carb on it with small electric fuel pump.

ENORMOUS mistake.

 

[Pappy G]

1. I am going to pull the cap off today. I don't think it is the problem though or it would not have started when I changed crank sensor. Yes I have spark. Timing was fine when it quit. No reason for it to be out of time now?
2. I get a couple 02 codes I expected that.
3. It has the spider injection so I dont know about if they are spraying for sure. Not sure how to tell to be honest.
4. I do have an egr code. I plan to pull it and clean it real good today.
5. Yes, the auto to 4 speed was an absolute night mare. Once we figured it out, we only had to put 2 wires together for it to run. Then of course run new wires to the activator on front axle.

 

[Schurkey]

1. I am going to pull the cap off today. I don't think it is the problem though or it would not have started when I changed crank sensor. Yes I have spark. Timing was fine when it quit. No reason for it to be out of time now?

If the distributor gear is heavily worn, rotor-to-cap alignment would be affected. This would show up in the cam sensor signal / crank sensor signal alignment, perhaps called "cam offset" on the scan tool.

Any chance the crank sensor WIRE HARNESS is faulty? You disturbed it when you changed sensors, and it worked for awhile. Then maybe it vibrated into a position where the wires don't make contact and the engine died?

2. I get a couple 02 codes I expected that.

You can expect to replace sensors. If this is like typical vehicles, you're going to need ALL of them replaced. They get ignored, grow old, either set trouble codes, or don't work properly but work well enough to not set trouble codes. Unless you can prove they're working fast enough by watching for cross-counts or graphical display of their voltage pattern, you're best off to consider them "done".

3. It has the spider injection so I dont know about if they are spraying for sure. Not sure how to tell to be honest.

Connect fuel pressure gauge. Run the fuel pump, then disconnect power to it. Crank the engine. Does the fuel pressure drop as the injectors fire?

Are the spark plugs wet with gasoline? Maybe they're fouled with gas, which is why it won't run.

4. I do have an egr code. I plan to pull it and clean it real good today.

May have to clean the passages in the intake manifold, too.

Test the valve to assure it's not faulty.

5. Yes, the auto to 4 speed was an absolute night mare. Once we figured it out, we only had to put 2 wires together for it to run.

The computer isn't upset by not having shift solenoids and torque converter clutch to control? Weren't there sensors for trans input and output speed?

I kinda assumed that unless you updated the computer or software, that it'd be in "Limp Home" mode. I guess I'm wrong.

Then of course run new wires to the activator on front axle.

I thought the power and switching for that came off the transfer case, so it wouldn't be affected by a trans swap.

 

[Pappy G]

Had to swap transfer case to manual as well.
I don't think this far back had a limp mode. It should have taken 3 months to hit limp mode if it did.
Yes I have code for shift solenoids because there are not any now.

 

[Pappy G]

I have a scan tool but I am not real good at using it. It will show live data but that is is all greek to me. I think If I plug it into a computer it might tell me more.

 

[Schurkey]

Had to swap transfer case to manual as well.

My '88 and '97 have floor-shift transfer cases. Did your transfer case not come from a vehicle with the axle disconnect?

I don't think this far back had a limp mode. It should have taken 3 months to hit limp mode if it did.
Yes I have code for shift solenoids because there are not any now.

Limp-home mode goes back to the beginning of computer control, in 1980 1/2. MAYBE even before that, on fuel-injected '76 Caddys and '77 MISER Oldsmobiles...I haven't confirmed that.

So you haven't updated the computer due to the change in transmission?