Before I get started, this problem is in my 1989 4.3 TBI S10 Blazer. But I cant get any information or help over on their forums. So I figured I'd ask on here since I know it doesnt have to do with the size of the motor. I know theres more than a handful of TBI guru's over here.

I was driving to work the other day and I started up an incline and my Blazer just cut off on me. I had a bit more than a 1/4 tank of gas in it, so I didnt think it needed gas, but I walked up a ways and got some. I put about 5 gallons in, and it still wouldnt run.

It starts up and runs fine for about 5 seconds, but then it just dies like its out of gas. It usually diesels for a few seconds before dying.

If I spray gas into the throttle body, it will run better. But it still wont rev very high. I can rev it up to about 3,500 rpm. If I give it too much throttle at one time, it just dies out like its flooding with fuel. But if I ease into the throttle and feather it down, it will rev up a little. I watched the injectors while I had a friend start if, and they spray fine.

I've checked fuel pressure, vacuum at the manifold, everything I can think of. Even if a sensor tested okay, I changed it anyways. (I have another 89 S10 sitting right next to it for parts)

I've changed:
computers twice,
TPS,
IAC,
MAP,
Ignition Module,
ESC (spark control),
open exhaust (thought the cat might be clogged),
fuel filter,
vacuum when idle (14-16psi)
Fuel pressure at idle (11-14psi)
Good compression on all cylinders,
No coolant in oil pan,
no smoke from exhaust (i.e. no blown head gasket),
Plugs, wires, cap, rotor replaced 01/07 2300 miles on them,
Alternator charging at 13.9-14.1 volts,
No codes,
No backfires,
Pickup coil,
Re-timed everything just to be sure,


now, if I plug up the TPS sensor, but dont connect it to the throttle shaft, and hold it all the way open, the truck will start right up and idle. Its still a little rough, but as long as you hold that TPS sensor open, it will idle. If you hit the throttle, then it bogs out and dies again. I dont know what that really tells me, but it may help someone.


Does anyone have ANY ideas? I've talked to over 20 people that actually know about TBI's, 6 of which worked at Chevrolet dealers when the motors were really used in the late 80's into the 90's.

The only thing I havent tried is the injectors. I cant seem to find a solid answer on how to test them. I guess just check Ohms across the two poles?

 

'87

I would check couple of things:

1) Fuel pressure at RPMs other than idle (if you can) - it should stay near idle value. If not you may have a weak fuel pump or pinched supply line. Check both supply and return lines for restrictions or funny looking bends.

2) Check TPS sensor for a 'dead' - worn out spot. A TPS is nothing but a variable resistor, but over time they may develop worn spot - especially around area just above idle. Take TPS off, measure it with DVM while slowly rotating. Look for sudden jumps in resistance value. I would go to J-yard get a unit together with a piece of harness for this test. It is easier to have a spare and harness for this test. A good TPS should change linearly 1k to 6 kOhm.

3) Your idle vacuum should be 14-16 in Hg not psi - I guess it is a typo.

I hope this helps //RF

 

Yeah, its in HG. I always look at the big PSI written in bold on my gauge. (I got that Actron POS that tells vaccum and fuel pressure on the same side)

I've changed the TPS sensor, but havent tested the new one for problems. I would assume that it wouldnt be bad if I just bought it, but its some japanese piece of crap, so I'll go test it to be sure.


I cant find my noid light right now, but I will borrow one from a friend tomorrow. I know it sprays fuel until it has completely died, but the pulses may be bad (i.e. computer or wiring), though I've changed the computer with 2 others that I have that are known to work.

I need to figure out a better way to test my fuel pressure too. I just have a T-fitting and a piece of rubber fuel hose going to a gauge. I dont think its very accurate.

 

'Formula87

Check TPS voltage output, Pin B of the TPS (Dark Blue wire, #417). At idle it should read 0.52 to 0.60 volts. As throttle is advanced from idle to WOT it should increase up to about 4.2 volts. Connect scanner or ALDL cable with your favorite scanning program and the two should track each other. If not then you have to check your harness, ECM connector, etc.
Pin C is +5 Volt Reference - Gray Wire
Pin A is GND - Black Wire

//RF

 

TPS is within range. I have checked and re-checked connections and ecm hookups.

I picked up a coolant temp sensor today at work, its about the last thing I can try.

 

'Formula87

I do not like to give up.
Couple of ideas worth checking. I've re read your original post.

One thing that caught my eye was the fact that your engine diesels before coming to a dead stop. Typically, dieseling is due to timing way over advanced. Since you have re-checked timing (and adjusted to spec) under normal circumstances dieseling should not take place. The only other way is for timing to be way off is for harmonic balancer outer ring to move excessively which is known to happen. I would check position of # 1 cylinder at TDC vs. timing mark on the balancer. Try to move outer ring of the harmonic balancer by hand. If it moves from hand pressure it is shot and must replaced. The second possibility timing chain slack or if timing chain somehow jumped a tooth? How many miles you have on this engine?

CTS can be checked with ohm-meter (DVM). At room temperature (25C) it should read around 2.78 kOhms

//RF

 

Well I had this weird dream last night that someone cut my brake lines, so I went out today and looked at my fuel lines, and sure enough, there was a big crimped piece of pipe.

It was closed enough to push fuel pressure through, but not enough actual flow.

How in the world a fuel line that runs along the frame rail got crushed, I dont know. But I changed it out with a new piece of fuel hose and clamps and it runs like a champ.


Just thought I'd let everyone know what it turned out to be because nobody ever tells you what happened when they get their cars running.

 

Thanks formula87

It was pinched fuel line after all.... //RF