I started a thread on this problem a while ago but I've narrowed the issue down since then (wanted to cut the cruft) and was hoping to get some more insight.

When it is hot out (or if the car runs for 10-15 minutes and then you turn it off) it will intermittently not start. When turning the key to "on" you will hear the main relay click but will NOT hear the fuel pump whir (you will also hear the 2nd relay click where the pump would have stopped whirring, were it running), then turning to "start" will turn the engine over but it will not start. If you hear the fuel pump whir when you turn the key to "on", then turning the key to "start" will cause the car to start (100% guarantee). Once the car is started it will run indefinitely.

It's also worth noting that if you turn the key to "on" and you hear the pump kick on and then wait for it to turn off before turning the key to "start", the pump may not kick on and it won't start. So to make this magic work I generally listen for the pump when turning it to "on" and then just turn it over. It's become such a habit that I do it in other people's cars as well.

It's always hard to get this problem to happen when I'm in my garage. But I have managed to test for spark and fuel and found that when this issue is happening I am getting spark at the plug and no fuel out of the line running into the engine compartment.

This has been an issue for about 1.5 years now. In general it's bearable as, turning the key back and forth, you will eventually get the fuel pump to kick on and then just turn it over. But it can be pretty bad in hot weather after sitting in the sun all day (I've spent a bit over 60 minutes on a few occasions). I generally try to park in the shade if possible, but if it's 90+ degrees out there's nothing you can do.

Here is a list of parts that have been replaced in the last year either as an attempt to fix this issue, to fix other issues (but related to ignition), or as general maintenance:

• Main Relay
• Fuel Pump
• Spark Plugs/Wires
• Distributor Cap/Rotor
• Ignition Coil
• ICU (Ignition Control Unit)
• Ignition Switch
• Battery

In addition I have:

• Cleaned up the g101
• Cleanud up the ground from the motor to frame
• Cleaned up the ground on the gas tank
• Inspected wiring between fuel pump, gas tank and chasis
• Pulled apart the ECU to check for damage, scoring, checked connection pins
• Checked connections at bulk heads
• Checked connections around distributor

I'm really at a loss as to what could possibly cause the fuel pump not to come on so I'm hoping someone on here will read this and say, "yup, I had these exact symptoms and it was X." or at least get me pointed in the right direction. All the indications point to a relay of some kind but unless the Main Relay I replaced had the exact same symptoms, I just don't know. I don't really know how to test electronics stuff but if anyone can point me to a good (and simple) resource I'm happy to purchase equipment (within reason) and test some stuff out. I would like to learn about this stuff while I'm fixing it.

No funky mods have been made to this car. It's just a straight up, sturdy, good gas mileage, daily driver. All parts are replaced with factory or OEM when needed.

At this point I'm almost willing to take it to a mechanic and dish out the cash to just be done with it. But sometimes (especially when you're looking for it) it will start fine for you no matter how hard you try. So my guess is they wouldn't find anything or they would think they would find something, hand me the bill, and then it will happen again in a month.

Any help would be greatly appreciated.

 

Not sure if I can relate, but had almost the same problem, two months back that my car would only start intermittently then get really annoy when at the gas station right after I pump gas, I would HOPE that it start, sometime it does sometime not and have to wait a bit.

After I change my main relay it start fine, then at time it don’t even want to turn over, then if I wait and play with the ignition it would start fine. Thought it was my ignition switch or my clutch switch, and batt seem to be fine, BUT when bring into the shop to have the batt test, it failed based on the temperature in the batt. Replaced the batt and now start every time. I am guessing that the batt not giving out enough current to some relay to make it start, but it a try.

 

That sounds very similar to the symptoms I've been seeing. Since I was planning on replacing the battery soon anyway (It's been 7 years and 100k miles) I just went ahead and did that this morning.

Let the car idle for a while, didn't have any problems. I had to run some errands so I took it out, made 3 different stops, and tried to do everything in my power to get it to not start. I never had an issue. So it's looking good but like I said, hard to say until I've gone a good week or so without issue.

Thanks for that tip. At the very least it's firing up faster than it used to so I'm sure the battery needed replacing anyway. I'll keep you posted.

 

Glad to hear..

 

Unfortunately, that wasn't the fix for me. Was out last night and stopped at Taco Bell on the way home. When I came out with my burrito I turned the key and did not hear the fuel pump; engine turned over but did not catch. After a few back and forths it kicked on and started up.

It's really hard to debug in this cooler weather.

Any other thoughts?

 

When it is not working, note if the CEL cycles on and off like it should when you turn the key on but don't crank. If the CEL stays on steady and the fuel pump doesn't run and you're absolutely sure the main relay is OK (even if it's a new one, resolder it), the ECU could be bad.

 

Well, you're not gonna believe this. It turns out I have not replaced the main relay.

When I first started having these problems everything pointed to a relay. Searching around online it seemed this generally turned out to be the main relay. I ordered one from the parts store. When it came in, I replaced it.

Last night I was on my back with my head under the dashboard looking around when I saw a box with the word "Main" on it. I maneuvered myself a bit so I could see the whole thing: "MITSUBA / RELAY ***'Y, MAIN". I put my hand to it and felt it click when I turned the key.

The part the parts store sent me was this: http://www.partsgeek.com/assets/dima...58-1023625.jpg

That relay is ALSO just behind the hood release so I thought nothing of it and putting your hand on it you can feel a faint click when turning the key because it is close enough to the main relay. I don't know exactly what that relay is now but, incidentally, partsgeek.com also has it listed as a main relay.

I removed the main relay assembly and lifted the relay from the housing. I'll resolder the connections this weekend and let everyone know how it goes.