1994 Accord LX 5sp non VTEC 240k miles
I've got an intermittent no-start that seems to be fuel pump related. Normally, when I turn the key to the ACC II position, I get the two second CEL light and a hum from the pump and the car starts right up and runs fine. On days when it doesn't start, the CEL stays on during cranking and the pump does not hum. Sometimes leaving the key in the ACC II position for 15 seconds or even 2 minutes will cause the pump to finally hum and it fires right up. It has never died once running.
I have repaired the Main Fuel Relay, then replaced it, twice, and bench tested the last one. I have checked all four main body electrical grounds. I've placed a VOM at the pump connection and verified, hum=12v, no hum=no voltage. I replaced the ignition switch. I checked during a prolonged no-start with stating fluid and the car ran till the fluid ran out. I've checked for codes with the OBD1 jumper and only one time got a MAP Sensor error that went away the next time it started. I've verified fuel pressure at the rail- 35lb running and 38 at pressurizing. I finally went and bought a used ECM but have not installed it yet as I can't get the car to not start today. Anyone got a clue?

 

I had same symptoms on my 94EX Auto. Fuel pump developed a "no-start" position even though it had power. Probably a carbon brush issue. I found that hammering the fuel pump w/ repeated on/off/on of keyswitch would eventually kick-off pump and get engine to start.


Replaced fuel pump to fix.


good luck

 

Thanks Texas
I had thought the same thing except the is no voltage present at the pump when it doesn't run: It seems that there is no signal to the pump or at least a very delayed signal when it won't start. I've even stopped trying to start it most of the time. if I hear the pump, it will start. if I don't hear it, it will not. Got anything else?

 

Are you sure you're testing for power correctly. The fuel pump is only hot w/ key in On position for 2-3 secs, then MFR opens and power is off.

I rigged a tell-tale light to the fuel pump power wire and back to the cabin through the rear seat to confirm power was getting to the fuel pump and no fuel pump action.

If you're sure you're not getting power to the fuel pump, then perhaps ignition switch assy is faulty. However in this case you should see dash lights off also.

Outside of MFR or ignition switch, you need to check integrity of wiring from MFR to fuel pump and local fuel pump ground.

good luck

 

I was testing using a VOM back pinned to the connector at the pump's access panel in the trunk. With the seat folded down, I could look at the meter and the CEL almost at the same time. When it would start, the VOM and the CEL were timed together and the pump would hum when the meter's scale reacted. On the days it wouldn't start, I could see no voltage, hear no hum and the CEL would remain lit. Then it began just delaying the connection by 10sec or even 2 minutes. I would turn the key to the ACC II position and watch. There would be no hum or voltage and the CEL would stay lit until suddenly it would all go right and I'd hear the pump, see the voltage and the CEL would turn off.
I'm almost thinking there is a corroded connection that is heating up as the voltage is applied (somewhere upstream of the pump) and the heat is drying out the connection til it makes sufficient contact to allow the full current through. I checked the ECU to see if there were burned spots, and it has none- it looks pristine.
Thanks again for your help.

 

If the intermittent "no start" occurs does it crank and sometimes fire but die? If so and/or regardless, if you have not replaced the electrical portion of the ignition "the switch" then that is a likely cause. You can check it if you have the circuit diagram, but be aware, an intermittent problem may not show when testing, as it is intermittent... It is a wear and tear item and eventually the contacts in the switch start acting up and it needs replacement. Sometimes when the car won't start if the person wiggles the key while cranking it the car will then start. If that is the case it is almost always the switch on the key cylinder.

 

Thanks Turtlehead,
I have replaced the ignition switch as well as the key cylinder (different issue), the MFR (twice and done a bench test with a VOM and battery to the one currently installed) and done a tuneup with plugs, cap and rotor.

When it does not run, it will spin the starter freely but not fire at all. As soon as I hear the pump hum, I know it will start. I have not yet experienced where I heard the pump hum at ACC II and had it not start. It has also never died after starting as though it was fuel starved or the coil was failing.

When it does not run due to no pump hum, stating fluid will fire it right up.
A while ago, it had a similar issue but only when the weather was really hot (i.e. 90deg plus). I cured that for five years by repairing the original MFR. I'm using AutoZone MFR's now as I got a bit over zealous with the soldering iron on the original part.

 

The main fuel relay is really two relays in one unit. The ECU is what activates both relays.

Depending on how much electrical testing you want to try, you can look for power at the #2 and #5 pin of the MFR. You would have to back-probe the connector. To give you a reference, the pins on the relay are numbered 12x3 on one row and 4,5,6,7 on another row.

The relay is grounded along with the ECU at G101. This is a ground bolted to the driver's side of the upper intake manifold. You may want to unbolt and clean that ground eyelet and bolt with a wire brush or sandpaper.

You can look for loose pins at the ECU.

 

I appreciate it PA
I've had the ECU out and pulled and reinstalled the connectors a couple of times to make sure they are making contact. I've gone through the G101 and three other main grounds and cleaned and replaced them. The ECU looked brand new; all the pins were straight and the board was clean enough to eat off of. I've got good ground at the black wire of the MFR. I've got continuity between the MFR and the pump's wire connector.




I have precious little hair left to pull out and this is driving me absolutely nuts. I can't get the problem to repeat reliably to even investigate. It doesn't seem to be humidity or temperature related. It will start 15 times in a row and then delay before starting and then not start. Some days I can't get it to not start. Then just as suddenly, it won't start for days.

 

Intermittent problems are a pain to diagnose. Your problem doesn't sound like an issue with the wiring from the relay to the fuel pump. It really sounds like a control issue. Now you will have to do some testing to eliminate possible causes.

You will have to be persistent. If you don't have a shop manual for your accord, the common diy thread on top of the gen tech help forum has a link where you can get a free pdf of the 94 shop manual. It helps a lot.

You may need to keep you volt meter hooked up to read voltage, so you can take readings when the problem occurs. A backprobe on the wire. Have volt meter set to read voltage to ground always hooked up to get a reading when the car acts up. Another test would be a voltage drop test along the wire. I can give you some more information on where to test.

A1, A25, and B7 are pins on the ECU that are connected to the main relay. I'd carefully check the pin on the ECU and the pin in the wire harness.

I don't want to point towards the ECU as the culprit, but did you replace the ECU?