Hello everyone. I have a 93 civic Si with around 210k miles and the original d16z6 motor on it. I have been having trouble recently with the fuel pump not priming sometimes. I ruled out the fuel pump itself because when it starts up, it runs till I shut it off. It has never choked out. I also check the thermostat housing where the fuel pump is grounded to and it seems fine. The main relay is also fine. I have a moisture problem in the footwell behind the passenger seat. I recently replaced the sunroof on it but I have never noticed any leakage from it. I dont really have any other issues with it running except for the iacv having trouble adjusting when I use electrical components. I have been racking my brain trying to figure this out so any help would be appreciated.

 

Have you resoldered the main relay?

Fuses 24 and 31 good?

 

O yah I forgot to mention all the fuses are good. I'm sorry not sure what you mean by resoldering the main relay. I Got a working relay and plugged that in and same issue still occured ha. Should I consider resoldering?

 

If a known good main relay didn't solve the problem, then look elsewhere.

Did you voltage test fuses 24 and 31? Click the Fuse Testing link in my signature.

Any CEL codes? Does the CEL stay on when the key is turned from off to ON(II)?

 

I had the same problem with a 93 del sol si D16Z6.
Borrow a known good P28 ECU and hook it up.

Moisture/condensation knocked out the circuit board in the ECU and the fuel pump won't prime when cranking.

This is a common problem.
The P28 ECU has 2 versions for a stick or auto transmission.

 

@Ronj@ht
-Imma get back to you on voltage tests but no it does not throw any CELs but it does remain on after I turn ignition to on(II) which I thought was an indicator other than noise that the pump aint priming.

@delsolintegra
-I will do that to knock out possibilities but if condensation got into the ecu wouldn't the car not run at all? I can get the fuel pump goin after letting the car dry a couple days and the car runs fine after that. Sorry if any questions sound dumb but still kinda fresh at the whole wrenching thing haha.

 

The moisture just seems to effect the starting circuit on the circuit board. I know it sounds odd but that's how it is. People who rework these ECUs and know more about it than me say it's common especially in humid climates. I've opened up my old ECU and I can't see any damage on the board but I'm no expert. It makes troubleshooting difficult. I spent over a year chasing this problem. With a replaced ECU I've been good for over a year and it was after a rain when mine didn't work also. I paid $135 from a junkyard. Good luck.

 

Yeah I guess i will try that then ha. Im gonna have to find this leak too if I don't want this problem reoccuring

 

 

Sorry havent been able to voltage test with the hurricane blowing. I will post the results as soon as I test.

 

The voltage tests came out positive so fuses aren't bad.

Quick question: Are you supposed to hear the fuel pump when it primes?

 

you can hear it from the back of your car making a noise like a compressor for about a second.

 

Okay i was just checking to make sure that the noise was normal.

 

ECU trust me.

 

Does your trust come with a money back guarantee?

 

Borrow one from a friend

 

Okay sorry for the no updates. I had finals on top of a family emergency so life has been hectic recently. I voltage checked fuses 24 and 31 both come out positive. I did notice however that 24 and a lot of other under-dash fuses dont get power when I switch the ignition to on(II) position. Could my problem lie within the ignition switch itself? My car has since been started but is not reliable enough.

 

When the engine will NOT start:

1) Does the fuel pump prime?

2) Is there spark at any of the 4 spark plugs?

3) Are any CEL codes recovered after cranking the engine for 30 seconds and jumping the service connector?

If the answers to 1-3 is no, then remove the G101 ground and clean it with steel wool and then tighten. If the problem persists, swap in a known good ECU to see if the problem is eliminated.

 

Havet posted for a while but it turned out the ecu was not sending a signal to the main relay for priming. Replaced the ecu and all is well. Thanks to all who replied.

 

you're welcome