I put this in the electronics section and got no replies, that helped at least. Anyway, got a 91 fbd that won't start. Has no injector pulse and no power to fuel pump. Anyway, the first problem I want to tackle is the injectors.

- I have constant 11-12v on one wire on both injectors. The other wire on both sides has no pulse.

- Checked ICM..good

-Checked for security light when cranking....comes on five seconds then off, no blinking. So vats is good. (Also it cranks)

Now my question is, do I need fuel pressure to have injector pulse? I doubt pressure would affect electricity? Would it?

If thats not the problem what else do I do? Cut my wiring harness open and trace wires to computer and test where it goes in at? That seems like the last logical idea to me.

Somebody Help!!!

 

Are you getting fuel spray from the injectors when cranking?

How did you confirm the ECM was good?

You also need to confirm that the HEI module in the distributor is good. If it is bad the injectors will not fire. The module inputs a signal to the ECM telling it to fire the injectors.

The Lt GRN and Lt BLU wires from the injectors go to the ECM they will not have a voltage on them unless the ECM is firing that set of injectors.

Yes, you do need fuel pressure to fire the injectors. However this is an indirect path. i suggest you put the fuel pump relay connector at the relay. Terminal C which should have a DK GRN/WHT wire to it should show 12 v or light a test lamp when you crank the car. I fyou don't see 12v here you have an open circuit in this wire back to its connection at the ECM, Terminal A1. This wire power the realy coil. When energized it sends power to the fuel pump. It also provides an input back to the ECM letting it know the pump in energized. You should see a code if the fuel pump relay is not working.

One other circuit ground that may cause a No Start condition is the white wire connected to terminal D of the HEI module. Pull the connector at the distributor, with the engine off and the battery disconnected, and connect an ohmmeter between terminal D and ground. A short circuit will give you zero ohms, while a good circuit will give you some large ohm value.

Check these out first, before you start tearing apart the wire harnesses.

 

Re-read my post. I have no fuel pressure in my lines--so no, no spray..Also there is no pulse, so thats another reason it is not spraying.

And the module in the dist you are talking about is the i.c.m (ignition control module)..I brought it to autozone and had it tested three times just to make sure

Also my ecm IS good..My car was running fine..then I did a headswap now the injectors have no pulse..And I plugged EVERYTHING back in where it was originally.

I have a feeling this is all originating at my computer. I think for some reason, my computer is not sending the injector pulse signal. All i did relating to the injectors was unplug them and plug them back in a week later. And now no pulse

 

Let's start here, send me your injectors, I'll test them and let you know if they are any good. No charge.

now, that aside, I don't think the injectors are your problem

What I have seen after a head swap is an interrupted ground. Injectors fire on a ground signal, like a relay. I assume you went to aluminum heads, make sure you have a ground strap to the block.

Check all your grounds.

As far as the fuel pressure goes, this is fuel pump 101. I have too many wires in my head for too many different cars, but on the GMs there is typcially a fuel pump test line somewhere in the harness, on the drivers side typically. If you have no pressure, you have to first determine if your pump is good.

Weird things happen when you take things apart sometimes. Probably the best thing to do is walk away and come back later.

 

Do a key-on, engine-off. Does the SES light turn on? Does the fuel pump do the 2-second prime? If not then check the fuse under hood. This in an inline fuse that powers the ECM & fuel pump. It is located near the battery and is inline with a heavy gauge wire that runs along the passenger wheel housing under the hood.

RBob.

 

I never had one of these to begin with.


As far as grounds go...all grounds are..well grounded lol..so im thinking what i need to do now is locate the holes on my comp where the injector wires go and test them? Wont that tell me if it is ecm related?

 

A SES light? OK, but you should still check the inline fuse.

Since it was a head swap, were all of the ground lugs reconnected to the back of the cylinder head(s)? These grounds are for the EFI system.

RBob.

 

no ses light..not sure why, especially with all these problems. I dont have that inline fuse though and never did since i bought the car..and the ground lugs are connected, but loose since i dont have a small enough bolt to make them tight...but even with them tight (pushed by hand and complete contact with head) im still getting no pulse.

 

check the fuses in the fuse panel... ecm and inj. id start there then look at the fuel pump test wire to verify that is working... its a small red wire by the blower motor and the a/c stuff. should have a white connector on it. did you disconnect the oil pressure switch by any chance? without that hooked up you get no fuel pressure. it should be right above the filter housing on the side of the block.