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Oh, Fuel injection, I hate you so much right now...

R

regular guy

Basic User
City
Cameron
State
NC
So I've got a 4.3l Vortec out of a 94 S10 in an 83 Scrambler. The scrambler was parked and stored for 7 months very recently The issue I'm running into is that every morning, it won't start. It just cranks and cranks. I pull off the air intake and shoot some starter fluid into the intake manifold and then it fires right up. I am on my third tank of gas since being stored so bad gas is out. It has now developed the habit of stalling out when the clutch is pressed in too quickly during down shifts. I ran some STP injector cleaner through it with no result.
I replaced the fuel filter and changed the fuel pump hunt from passive to active. The s10 TSM says its in the gas tank, the 82 jeep TSM says it's engine mounted. I traced the lines (3) from the gas tank (33 Gal aftermarket) to the engine with no pump installed. On the top of the gas tank the fuel lines appear to originate from a sending unit, but I'm not going to be able to verify that until I drop the tank. One line goes to the vacuum canister and the other two go to the back of the engine to the left of the distributor. The supply line does run across the top of the transmission (Would this get hot enough for vapor lock?)
I read up on all the idle issues on the s10 forums and I checked the spark plugs (all appeared normal and all cylinders firing) and i checked the ignition coil with a multimeter per factory manual.
Other potential causes according to the inter webs could be the EGR valve stuck open (exhaust to intake emissions crap), mass air flow sensor, O2 sensor, PCV valves (getting replaced tomorrow) and vacuum leak.
I do not have a vacuum gauge but checked all the connections were tight and sprayed with carb cleaner looking for bubbles. No cracked or rotted lines and everything appears to be in good shape.

Any hints, tips or tricks I'm missing would be greatly appreciated.

This is not the TBI model, it's the CPI engine.

Otherwise, more troubleshooting tomorrow and start replacing parts.

Also this is an OBD1 system with no codes displayed.... helpful, I know.
 
I would check the fuel pressure, if the 4.3 is like the 5.7 the pressure is vacuum regulated. Maybe a bad regulator? Does the pump run when you key on or crank?
 
I was going to throw out vacuum leak, could be fuel pressure but I would think it wouldn't have really run right at speed too.

Not sure what spraying for carb cleaner looking for bubbles would do, it's a vacuum leak, so no bubbles, right? Air is leaking into the engine, not out. Vacuum gauge isn't really useful for finding leaks unless you have very few lines and the issue may be a connector you don't end up testing or a joint between two parts, not a line at all.

You could use the starter fluid when the engine is idling and **COLD** to spray around or you could wave a slightly opened propane torch and listen for the engine revs to change.
 
Without dropping the tank, I haven't found the fuel pump. An in-tank fuel pump is about the only option left. It's not mounted anywhere else that I can tell. It would make send about the vacuum regulation due to fuel line number 3 running directly from the tank to the vacuum canister in the engine compartment
 
I misread the troubleshooting on the carb cleaner. You're absolutely right about starter fluid supposed to change the idle noise. I reread it last night. I like the propane torch idea as well. I'll try both of those and see if I get any change this evening.
 
Faulty IAC?

The IAC (Idle Air Control) should be mounted by the throttle body. 3 wires I think.
 
I'll be checking that this evening as well. I've read about the IAC causing problems similar to what I am experiencing.
 
The 94 CPI engine had a design flaw. That is why chevy went away from it so quick. The EGR valve collects carbon and sticks open. It cause hard to start and rough idle. Really rough idle. Even if this is not what is causing your problem I will one day cause a problem. The after market has a fix. It's a gasket for the EGR that has a metal screen built in. It's a cheap way to fix your problem or eliminate it from happening down the road.
 
When you get it started in the morning, does it start ok the rest of the day? If it does, try turning the key to the on position for about 5 seconds, turn off, then turn on for 5 seconds. Do two or three times. If for some reason the fuel pressure bleeds down from sitting over night this will get the pressure up to operating pressure. If you turn the key on and just crank the engine, after about 5 seconds the fuel pump shuts down (for safety since engine didn't start). Had it happen to me just a thought.
 
Thanks for all the input. This problem is put on hold because I started the transmission/ transfer case rebuild today! When I have it back up, I will try the key trick. replace the PCV valves, pull the EGR and clean it and see what makes a difference. IAC from there and if that doesn't fix it, we go to a whole new can of worms.
 
LetchcoreCJ7 said:
The 94 CPI engine had a design flaw. That is why chevy went away from it so quick. The EGR valve collects carbon and sticks open. It cause hard to start and rough idle. Really rough idle. Even if this is not what is causing your problem I will one day cause a problem. The after market has a fix. It's a gasket for the EGR that has a metal screen built in. It's a cheap way to fix your problem or eliminate it from happening down the road.
Click to expand...

Who is the maker of the aftermarket gasket? Google fu failed me. never mind. Found it.


I'd like to go back to a 258 carb setup, but 20 mpg says no
 
With my 4.3L setup and 33 gallon tank I drive 600 miles between fill ups. It's hard to argue with numbers like that.
 
I drove a Volkswagen 'up!' through Italy last week, I got about 600 miles on a 50 liter tank. Maybe you could drop one of those 3cyl engines in?
 
So I got back to this issue today. Removed and cleaned the EGR valve and replaced the PCV valve. Still having stalling issues when going from high (2000+) rpm to idle (Pushing in clutch.) I am thinking the next thing I will do is replace the IAC sensor, possibly the O2 sensor and, if absolutely necessary, the EGR valve itself. Little bugger is spendy!
 
Has anybody ever messed with the idle screw? It sure sounds like the throttle blades are too closed and it's idling mostly off of the iac. You should be able to plug the iac opening and the rpm should drop to near 500rpm. I'll bet that yours will not. If you had a scanner you could read the iac steps instead.

Sent from my SCH-I545
 
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