1991 Lumina, no start

#1

We got this '91 Lumina off of a wrecker yesterday. The owner had already replaced the in-tank fuel pump with a new one in an effort to make it run. I don’t know if he checked for fuel pressure before replacing the pump.



It will run if starting fluid or gas is shot into the area of the butterfly, so we know we don’t have a spark or timing chain issue.



It must be a fuel issue. But:



It has 43 lbs of fuel pressure at the fuel rail.



When we check with a test light at the two fuel injectors that can be seen without removing the manifold the test light comes on. That leads us to think that there is power to the injectors.



If we depress the schreader valve on the fuel rail, we get lots of fuel. That would indicate that the fuel rail is not full of air.



We replaced the ECM with another from a running Lumina. They had the same part number.



Anybody have any ideas what we should check next?

#2

Do you know the history of the car? Did it sit anywhere for a long time not running?

I would next suspect the fuel injectors themselves - I’m guessing that by a test light for the injectors you mean a noid light so you know power is coming through the harness. But one or more of the injectors themselves might be dead. They might also be clogged, esp if the car sat. I’d put a meter on the injectors to check resistances and if those show ok probably pull the rail and check for spray pattern. Of course, it might be easier to try starting it for a while and then pull a plug or two and smell. If you don’t get much fuel smell the place left to go is the rail & injectors.

#3

Is this the pressure that is called for? I am thinking wrong pump.Make sure pump is matched to injection type (like a pump for TBI used on a CMFI system)I am not sure when CMFI came into use.

#4

This must be a 6 cylinder engine with the fuel injectors under the intake manifold. Only two (maybe three) of the fuel injectors electrical connectors can be disconnected for checking with 'Noid test lights.
The foremost suspects are faulty fuel injectors. To get to the fuel injectors, you’ll have to remove the intake manifold. On this era of Chevrolets, the fuel injectors are wired three fuel injectors to each branch (two branches). So, three fuel injectors fire at once.
Don’t tell anybody I told you this: you could test the fuel injectors by disconnecting their electrical connectors, except the one to test, place a fuel injector into a clear container, crank the engine and watch the spray pattern from the fuel injector. Test all in a similar manner.

[ Keep all the fuel injectors connected to the fuel rail for testing; but, disconnect their wiring.]

#5

It did sit for a period, but ran for several months after that.

We only checked them with a test light to ground. What should the meter read, and is it hooked up with the injector lead disconnected? We did not disconnect the two on either end we could get to.

It would seem that if only some of the injectors were plugged, it would try to run on those that weren’t.

#6

I THINK it’s the right pump. It’s what the owner got at his favorite parts supplier. The V-6 has six injectors fed by the rails.

#7

I’m not familiar with the term 'noid test lights. We only have one the clamps to ground with a sharp probe on the other end. Do we need to buy another tool. I do have an ohmmeterif that will help.

#8

As suggested… you need to see if the injectors are being pulsed. Battery power is supplied to the injectors and the ECM grounds the injectors to fire them. You need to get the test noid to see if the injectors are being pulsed.

If they are not firing there could be a number of reasons why. The first and most common problem on this vehicle is shorted injectors. If just one injector is shorted out it will take out a quad driver in the ECM, so the injector and ECM would need to be replaced and I would recommend replacing all 6 when you are in there.

#9

You can get 'noids [a brand name for LED test lights which plug into the electrical connector to each fuel injector] from auto parts stores (or, check ebay).

#10

Since you have multiple electrically controlled injectors it is not TBI and it is not CMFI. I am betting on multiport fuel injection,you must find the fuel pressure sec. for your type of fuel injection (at least for my benifit) I am suprised multiport was offered in 91 and that the spec is 43 psi,I will try on my end to sort this out.

#11

OK, we borrowed the noid testers on Autozone’s tool loan program. The injectors do not pulse. Does this mean that we have destroyed the ECM we borrowed from another '91 Lumina?

#12

Yes, it’s possible the ECM from the other car was detroyed. Did you try to reinstall it in the other car to see if it runs?

What you need to do is get the diagnostic chart A-1 to A-3 called “engine cranks but won’t start”. It will give you step by step intructions on what to do.