No Fuel.

93ChevyZ71 · Jul 17, 2024

Hello, I have a 93 Chevy Z71 and it was turning over, but not starting. Had spark, so we checked fuel. Dropped gas into the TBI and it started so our problem is fuel related. The fuel pump was not priming when opening the switch, but it worked when we sent current to it ruling the pump out. No blown fuses. Replaced the relay and It only “clicks” when we send current to it. Checked all the wire fuses on the power rail and they all had continuity. So we figured it was ECM and we just replaced it and still the fuel pump doesn’t prime and the relay doesn’t click on opening the switch. Our next guess is the PROM chip inside the ECM housing. Can anyone help with some ideas? Thank you

docstoy · Jul 17, 2024

Usually replacement ecm's don't have a prom/chip in them it has to be transfered from ecm that your replacing if purchased from a parts store, if purchased from salvage yard (used/salvaged) they will usually have a prom in them but is best to transfer prom from your ecm to the one that will be installed . Is your ck engine light on with key on ? And that is if you have a ecm with prom installed . Service / diagnostic information is available from sticky thread above it is titled 88-98 service manuals, you need to look at fuel and emissions manual and look under symptoms for your problem and that will get you started. Welcome to forum and best of luck

Komet · Jul 18, 2024

Did you send +12v to the pump from the relay location, or somewhere closer to the pump?

93ChevyZ71 · Jul 18, 2024

Komet said:
Did you send +12v to the pump from the relay location, or somewhere closer to the pump?

To the relay

93ChevyZ71 · Jul 18, 2024

docstoy said:
Usually replacement ecm's don't have a prom/chip in them it has to be transfered from ecm that your replacing if purchased from a parts store, if purchased from salvage yard (used/salvaged) they will usually have a prom in them but is best to transfer prom from your ecm to the one that will be installed . Is your ck engine light on with key on ? And that is if you have a ecm with prom installed . Service / diagnostic information is available from sticky thread above it is titled 88-98 service manuals, you need to look at fuel and emissions manual and look under symptoms for your problem and that will get you started. Welcome to forum and best of luck

93ChevyZ71 · Jul 18, 2024

Yes we used original PROM, so I guess we have more digging to do, thank you

Komet · Jul 18, 2024

93ChevyZ71 said:
To the relay

Ok so the problem is between the ecm and the relay. I am one of the weird people who have had a no fuel situation and it was actually the ecm (ecm wasn't grounding fuel relay, BMW Motronic 1.1) but it's usually not.

I'd splice into the fuel pump relay wire at the ecm and either give it +12v or ground it depending on what signal it's supposed to send. If that doesn't activate the pump, the connection between that location and the relay is bad. If it does activate the pump, then it's reasonable to conclude the ecm isn't sending the signal.

PlayingWithTBI · Jul 19, 2024

The Oil Pressure Switch on the China rail behind the distributor bypasses the fuel pump relay and will turn on the fuel pump without it. Either you have a blown fuse, a bad OPS AND relay, bad wiring to the fuel pump, a bad ICM, a bad pump, or a split hose connecting the pump to the sending unit.

No Fuel.

93ChevyZ71

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