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92 Civic - Fuel pump takes a long time to prime

My embattled 92 civic hatchback has developed an issue that makes it take forever to start. I put the key in the ignition, turn it to the start position, and then I have to wait for up to 10 to 15 minutes to hear the click-hum of the fuel pump priming (which turns off the check engine light) before I can start it. I’ve noticed that it’s much worse on wet days, but generally starts right up if it’s only been off for a few moments. I used to just give the Civic ample warning before I need to go somewhere by running out, turning the key to start, and then letting it sit there, but this is beginning to wear down the battery. I’ve replaced the main relay to no avail, and once the car is running it does just fine, which makes me think that the fuel pump is fine.

Full disclosure: this thing also has a bad oil problem. A diesel mechanic helped me change the head gasket several months ago (owing to yet another starting problem, and I’m starting to think it was the same starting problem, and that I blew the head gasket from trying to push-start the thing), and in our efforts, we seem to have messed up the valve cover gasket. There is oil in the plug wells, and there’s some power loss as the engine is trying to cough up the oil. I haven’t replaced it yet because it doesn’t seem to be a critical issue as long as I keep feeding it more oil. I’m not brave enough to crack it open on my own, but my brother in law has a standing invitation to help me when our schedules align.

I’ve done some searching on the web, and the general concensus of the internet (and the internet HAS to be right, right?) is a bad ECU. When I look this up in my manual, getting to the ECU is just a matter of pulling the carpet in the passenger-side floorboard out of the way. Okay, great. Only problem: I can’t find a place where I can buy a good ECU. I could probably find one at a junkyard, but there’s no guarantee there. If I do manage to find one, I want to be able to return it if replacing it doesn’t fix anything.

Fuel pump - checked before we changed the head gasket, came back okay
Starter - I changed it by myself before we changed the head gasket
Ignition Switch - The key is optional, but everything else electronic in the car responds properly when the switch is in the proper position.
Distributor/Rotor cap - Changed when we changed the head gasket

Please, oh mechanical geniuses, tell me it’s something simple…

Just because the pump eventually starts doesn’t mean its any good. I think its worn out and time to replace it. You can test it by checking for voltage at the connection to the pump. If you have voltage at the connector, the ECM is good and the pump is bad.

Don’t some Hondas have a problem relay that can cause this?

While the fuel pump is easy to get to (it’s under the back seat), it’s designed in such a way that I’d have to pull the thing completely out in order to test the voltage. The idea of pulling it out while on the sloped surface of the parking lot in front of my apartment makes me nervous. But I do live close to a fire station…

If it’s been running a while and I shut the system off, and then within a few moments turn it back on, it primes as if there’s no problem. I’d just take the thing to a mechanic, but my fear is that they’re going to charge me an obscene amount of labor because of the words “fuel pump” while the fuel pump is actually easy to get to. Given that it doesn’t take very long at all to prime once it starts to prime (once the hum starts, it never lasts more than a second before the light turns out), does that make it more likely that it’s the ECM?

I think @texases is on to something here. Just replace the Main Fuel Relay. It’s inexpensive and early Hondas are know for bad fuel pump relays especially when they get warm. Located under the dash on the left side of the steering wheel (If I remember correctly).

That’s the relay that I’ve already replaced. Sorry if I used the wrong term and caused some confusion there.

Temperature seems to have little effect. Humidity makes it worse, though.

I believe he said he “replaced the main relay” already. Otherwise that would have been a prime suspect.

Has the fuel pressure at the rail been measured? That’s one idea to consider. It does sound like a fuel pump problem, but it could indeed be the computer. I wouldn’t assume it is the computer though until all the appropriate fuel pressure and injector tests have been done.

BTW, running the starter motor continuously for 15 minutes is a bad idea. The car designers didn’t design it to be used like that. Worse case , it could catch on fire. Best case, you could quite possibly ruin your new starter motor, damage the flywheel, damage various relays, fuses, and wiring, and possibly damage the battery. I had a friend with a car that the starter solenoid contacts got stuck “on” and she didn’t realize it, parked the car on the street, went into her apartment, and 20 minutes later looked out to see what all the sirens were about. Yes, her car was ablaze.

Yes the relay has been replaced.

Pressure at the rail is interesting. When we did the head gasket (I say “we” loosely, since what I did mostly was hold things) we had some problems getting the fuel rail mounted back in properly. One of the new injector seals ripped, so we had to use an old one, and it doesn’t work that well. Could that be causing this? I can’t actually check the pressure at the rail, but I could probably handle replacing the injector seals on my own. Doing it while we’re working on that valve cover gasket would be convenient.

By putting the key in the start position, I mean the position on the starter that it rests in once the car has already started. The position that turns on all of the various devices that keeps an engine running. I’m not sitting there trying to turn it over for fifteen minutes. I don’t even think my battery could withstand that. What I’m doing is turning the key to the point where, normally, the fuel pump would prime, and then waiting for it to prime. Eventually, I can hear a slight hum as the fuel pump finally gets the message, and then the click that accompanies the CEL turning off. Once it’s started, it’s it’s normal, happy, oil-burning self.

Ok, that isn’t the “start” position, that is the “run” – edit: or “on” position. It is probably labeled where you put the key in.

I guess the question is: What determines when the pump is supposed to start with the key in “on” but the engine not running? My guess, the fuel pump itself is what decides when to turn on when the key is in “on” but the engine isn’t running. The other alternative would be the ECM measures the fuel pressure at the rail, but that would require your car to have a fuel pressure sensor. I doubt that was used in 1992. Maybe somebody here knows. Which engine do you have? 1.5 8 valve, 1.5 16 valve, 1.5 vtec, or 1.6 vtec?

No experience with you car – just a driveway do it yourselfer here – but I doubt the problem is the ECM. At least I wouldn’t assume that. First, measure the rail fuel pressure. I expect you’ll find it to be low. You’d have to look up the specs, but I’d guess the pressure would be about 35 psi with the engine idling and the vacuum hose connected. 45psi without the vacuum hose connected. If you indeed find the pressure is low, your mechanic needs to eliminate the following suspects which could cause low rail fuel pressure:

  • Fuel filter clogged
  • Fuel pressure regulator faulty
  • Pump check valve
  • Leaky injector

My seat of the pants guess is a bad pump check valve. Best of luck.

Check if your ecu is fried this happened to me!

5 year old thread. I would hope they have solved their problem by now.

1 Like

Did you find out what the problem was? I have the same exact problem on my 92 eg. Fuel pump takes anywhere from 5-30 minutes to prime when it rains. However lately it’s also been taking a few minutes to prime on normal days too. It’s been happening for the past 2 years but just never really look into it that deep and now it’s starting to really bug me! I’ve taken it to 2 mechanics and both couldn’t find what was causing this to happen. One of them said it could be your ECU, but it’s not worth buying another ECU and having the same problem. If you have found what was causing this to happen please let me know!

If you turn the key all the way on and you do not immediately hear the fuel pump prime…then it is your Main PGM/Fi relay… Or the wires running to it… You stated you replaced it…was it new? Was it extra cheap off the internet? They are not all created equal. But this issue is or will be fairly easy to troubleshoot since you only have one place to look for the fuel pump power during the prime phase… That is the PGM/Fi relay…

Unbolt the relay and let it dangle from the wires…turn your key all the way on…you should feel the relay click and hear your prime. If you don’t get that exact condition turn the key off and then back on again and tap on the relay as the key goes into the run position… try it multiple times you should be able to repeatedly prime the pump by cycling the key. You can find out if power is being connected via that main relay. If you are getting power to the pump and no prime, its your pump. But you will be able to figure all this out by monitoring that relay.