The 1994 VIN Z (TBI) has one issue with starting.

It applies fuel and base time ignition based on a basic map and temperature input in OPEN LOOP (referring to the IC only). At 400 rpm a signal is applied to the ICM and the vehicle control system takes over ignition timing.

In depth explanation on what I have learned from the manual:
We have two ways to control ignition. One is on the distributor itself the ignition control or (IC or ICM) and the other is the cars control module (CM) which also controls injection.

Not too clear what exactly happens in the respective boxes but it seems that:

- The IC on the distributor is able to trigger the ignition on base timing and advance a limited amount.
- The IC is the link between the CM and provides rpm and crank position to the CM.
- The IC above 400 rpm relays timing to the CM and is in charge of triggering spark at the correct time.

During startup it is ONLY the IC which provides ignition.
During startup it is the CM which provides injection.

This is the reason why we may have spark and fuel but either not starting or it dies as soon as it fires up (remember 400 rpm). If something is wrong with the IC or CM it dies.

Very hard to diagnose without a TECH I which may exactly tell us which signal is missing. Despite having the service manual it took some reading in the electrical and diagnostic to get it solved.

As soon as I had the new (reman) distributor in the vehicle it started up and runs fine.

Another issue found on some posts is that it quits after some 30 seconds. This may be indicative of a problem with the CM. Again very hard to diagnose without a TECH I. Such an issue may be able to store a fault code on the CM.

I would suggest the following DIY analysis.

- Remove Air filter assembly and check for fuel spray during cranking. (Take respective measures when dealing with open fuel and fuel vapors!)
- Place an ignition spark tester between one of the spark plugs and the distributor. (Take respective measures when dealing with high energy high voltage discharge ignitions)
If both conditions are fulfilled you MAY GUESS that the IC at least delivers the rpm signal to the CM and the CM is able to activate the fuel injectors. At this point I personally would rule out the fuel side of the problem in a first step.

At the same time we may rule out the ignition coil as we have spark. (The quality of the spark is another thing.)

At this point I would go for a tune up and replace:
- spark plugs
- spark wires (or at least number them all at the distributor (tape or something) and remove them and check on the full lenght.)
- distributor cap
- distributor rotor

Sometimes if you find broken cables, or other oddities this may solve the problem on the cheap.

The next step would be to change the distributor. But this requires:
- knowledge of how the distributor is fixed.
- note the position of the distributor frame in relation to the engine block and being able to translate that position to the new distributor.
- note the position of the finger of the distributor. (may turn engine by hand to position)
- taking note of the position of the no 1 cylinder (spark wire)
- a LONG screw driver to turn the oil pump and put the new distributor back in with the finger pointing into the same direction as the one removed.
- a timing light to adjust the base timing according the sticker in front of the radiator.

Good luck and get your Blazers running again.

Marc

 

Next time you ever have to replace your fuel pump assembly..I would purchase a fuel pump with a lifetime warranty.And no I`m not talking about buying a cheap fuel pump from autozone.Autozone crap has a lifetime warranty, but you`ll have to change it out once a year.A buddy of mine bought aa fuel pump from the zone..He bought the one with a lifetime warranty.After a year, he had to replace it.6 months later he had to replace the pump again.Napa sells great parts.if you have a napa near you..Get one from them.If not you can go on line to napa.com to purchase one.Also look up Summit racing .com or Jegs.com

 

Better yet, Get an AC delco or Delphi. Which are KNOWN to last in these vehicles.

Any aftermarket brand these things will eat like candy.

RockAuto sells those for a good price.