Before we all panic and start ripping out sensors and harnesses, try a few simple things.

Is there gas in the tank? You have classic 'ran it out of gas' symptoms.

 

Gas tank is full. I did some extensive testing. It seems the injector pulse is very weak during cranking after the car has been warmed up. I can spray carb cleaner into the MAF and it will start. I think the injector driver in the LH is failing. I checked the impedence of all injectors while warmed up. They measured between 16.4 and 16.7 ohms. Fine to me.

 

The car doesn't get (or need) a lot of fuel while cranking. But if the pulses are 'weak' rather than 'short', there are a couple things to do. first place to start is the battery well, where the power for the injectors starts. Make sure the auxiliary positive wires are firmly attached to the positive post connector on the battery. It's not a bad idea to disassemble all these wires, make the parts shiny and bright, and reassemble. Then go on to the fuel pump relay and the LH relay. These are both very common 53B Bosch relays, pieces you can find almost anywhere. You can swap them for the horn and intensive washer relays for now if you want.

'89 and later cars have a relay ID'd as EZK protection, used to isolate one bank of injectors if one ignition system fails. Since you measure the correct 16 ohms at each nozzle, you should have 2 ohms when measuring from the LH brain connector, 4 ohms for each side if measuring from the EZK protection relay. If you measured 16 ohms for the whole injector array at once, you have harness or connector problems that need attention.

HTH!

 

Bob, would you happen to have a wiring diagram or pin-out of the LH? I want to check the harness. When I was testing this past weekend, I measured 12v at both wires of a injector plug. Shouldn't I only have power to one side. The LH would ground trigger the other side to fire the injector, correct?

Thanks for your help,

Pete

 

Pete--

I have the wiring diagrams but they are paper not electronic. Jim Morehouse sells the whole WSM on CD. along with all the tech bulletins and specialty service manuals, for a very reasonable price. Perhaps someone will share an electronic version with you.

The LH brain does in fact pull one side of the injector circuit twoards ground to get the injectors to fire. One side is at battery voltage when the LH relay is energized, and the LH box has a few FET devices that switch the low side towards ground or let it float. Each injector has a nominal impedance of about 16 ohms, so the 8 in parallel would read 2 ohms at the LH plug. If you decide to measure between the power supply pin on the LH and each bank on an '89+ car at the EZK protection relay, you are looing at only four injectors at a time so 4 ohms would be expected per circuit.

There's an extended thread with diagnostic methods and pin numbers, in that case looking for a damaged harness. I'll try to hustle up the link. I spent an hour digging through wiring diagrams to get all that stuff worked out, and I'm rushing to get a few drawings out in the next hour or so so it won't happen again right away.

 

Pete--

Do a quick search for a thread titled "The Official Fuel Injector Thread", and follow it. My contribuions don't start until message 16 in that thread. Must have been asleep that day... Anyway, it gives you some things to try and the pins to diagnose the injector harnesses.