90HFSurvivor

I've had an ongoing issue for years in my 90 HF that I just can't seem to figure out. I've either had to leave it running, or find a hill to park on when the engine is warm or it's really hot out, LoL.

First, I've searched here, and I've searched other forums, and I haven't been able to find any scenarios that match mine.

A little background.... I've had three different engines in the car since I bought it in 98, and currently have the 16 valve 1.5 out of an old Civic wagon. I've replaced all of the cabin relays, and put a NIB OEM ECU in it, and nothing has changed. The ECU flashes the code for coolant temp sensor, and AIT sensor. I've replaced both of them and still no change. All grounds have been taken loose and cleaned with a wire brush. I've just used it as a work beater for several years, but now I'm in the process of restoring all of the mechanicals on it, and I'd like to resolve this issue.

When this happens, you can smell fuel like it's flooding itself. I assume this comes from the coolant temp fault, but as noted, the sensor is new, and the ECU itself is new. I've done the valve cover gasket, timing belt, axles, brakes/lines/master cylinder, new dizzy, plugs/wires, and doing a clutch and rear main while I'm in there this weekend. I've started gathering parts for a complete suspension and steering rebuild. After doing all of that work, I'd hate to still be dealing with this. Anyone have any experience with this or any ideas? It's been going on for years now, and I finally gave in and posted about it. Thanks for any input. Long time lurker, first time poster.

TacoCat

What do you mean by won't start? Crank but no start or no crank no start?

95_civic_gsr

My first thought is a main relay, since the heat would cause the gap in a cold solder joint to widen, and thus not make contact. But you say you changed all the relays in the cabin.

I was thinking if it cranked but didn't start, it could be something with the evaporative emissions, possibly a bug made a dirt nest in a hose that needs to vent. This happened to my 89 civic and fuel dumped all over the ground.

But if it doesn't even crank, maybe the AIT sensor has the wrong wire plugged into it. When I did my 89 civic swap to a JDM b16, that was the one thing I didn't do right to keep it from starting first try. It has a very similar plug on it, with a similar length of wire, as another sensor in the same area.

90HFSurvivor

Sorry, yeah, it cranks, then seems to flood itself and won't run. After it cools off, or first start of the day, it starts fine. Sometimes it takes up to a couple of hours after driving to start without a push/roll start.

90HFSurvivor

I changed the relay by the driver's side kick panel, and the relay by the steering column. All relays in the fuse box as well. From my research, the one by the kick panel is the main relay. Is that correct? Am I missing any?

It doesn't dump any fuel on the ground, just cranks and cranks like it's not getting fuel or spark. I've verified it's getting spark with the old screwdriver trick, and you can physically smell fuel. I'm stumped.

As for the AIT, I taped the proper plug as I unplugged it to avoid confusion. So I don't think it's that. Thanks for responding.

95_civic_gsr

I'd still try spraying a little starting fluid in the throttle body to see if its getting fuel. You could be smelling fuel from somewhere else. Maybe it doesn't have enough pressure for the injectors.

Also I've had one civic that after questioning the former owner many times, he admitted to hooking up an air compressor to the fuel lines to flush the rust out of the main fuel feed back into the tank. When I opened the tank cover and pulled the fuel pump out, the short 2" piece of hose between the fuel pump and fuel line had burst. I'm not saying that happened to you. but that small piece of hose could be bad, and sucking air instead of sucking fuel. Or at least not building up to the proper pressure the injectors need to atomize the fuel.

90HFSurvivor

Thank you I'll give that a shot. It's in pieces in my garage at the moment. Got the transmission out and the throw out bearing spring had both hooks broken off. Probably be Thursday before a new one gets here. Always something stupid........

Tyson

Because the overwhelming cause of not starting when it's warm is the main relay, and you've not been specific about it, I need to ask if you can identify what the main relay looks like. And what did you replace it with? Did you try resoldering the joints? Which is the exact fix, you really don't need to replace a broken one. Just reheat the joints with a soldering iron.

Do you know what priming the fuel pump sounds like?
Maybe try priming a few times by turning the key on, wait til it finishes priming, then off and on again.

Because you say you smell fuel, makes me think the injectors or something is leaking too. Causing air in the fuel lines.
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90HFSurvivor

I replaced the relay by the hood release latch, and the relay by the steering column. I replaced both with part numbers cross referenced from OEM part numbers from Rock Auto. One was a seven pin relay, the other was a four pin. Yes, I tried resoldering the joints initially, and when nothing changed, I bought new relays. Like I said, it's been an ongoing issue for quite some time. I've tried just about everything.....well everything I could think of.

Yes, fuel pump primes just fine. In fact, when I replaced a leaky line by the tank a couple of weeks ago, it was spraying out as soon as the key was turned on. So I've heard it all of this time, and visually confirmed that very recently. I will say that cycling the key seems to work when it's been parked and it's hot ambient temperature wise. But that does not work when the engine has been at operating temperature. It must cool down before the car will start.

It's not overpowering, but it smells as if it's flooded. As I mentioned earlier, I replaced a leaky line, and I haven't tried to start it in hot conditions since I fixed that. You could be onto something with leaky injectors. I'll give that a look when I get the transmission back in it.

Thank you for responding.

Tyson

Again, you still haven't identified the main relay. There's multiple relays near the side panel.

90HFSurvivor

To the best of my memory, it was a four pin relay. I'm at work at the moment, so I can't physically look. The other relay I replaced was was under the dash around the steering column. It was a seven pin. So if I'm missing some near the kick panel, where are they located? The one I replaced was directly above the hood latch. I didn't have a manual, I just read about the relay issues online and looked until I found a couple and replaced those after trying to resolder them. If I've changed the wrong ones, I'll sure feel stupid if I find the right one and it fixes this headache, LoL. Thanks for the help.

Tyson

It's not a 4 pin. It's very unique looking. And easy to search. Yet you say youve searched but can't seem to be bothered to actually Google "CRX main relay".

I'm trying to help you help yourself, but saying you already did everything and are still helpless is kinda pointless.

90HFSurvivor

Not everything I have looked at shows a seven pin relay. Some sources show a four pin relay. The only seven pin I found was under the dash near the steering column. I replaced it.

I never said I did everything. I said I did everything I knew to do. Reading comprehension is key. Those are the two relays I have found that are called "main relay". Then there's a fuel injection relay that looks a lot like the seven pin relay that I replaced under the steering column. The only relay I found in my HF by the kick panel is the four pin relay....also called a main relay by Google and Rock Auto. I'm getting confusing and different information. I've researched. I've read the main relay is by the kick panel, driver side. All I found in that area was a four pin. Rock Auto lists a four pin main relay for the HF. That's what I bought. When it didn't solve the issue, I bought the seven pin, rectangular shaped relay and it didn't fix it. Both have brackets that slow them to be mounted to the chassis. So, I asked, am I missing something that I'm not seeing. I've been polite and grateful for any help. If I wasn't stumped, I wouldn't have posted. What's with the attitude? I can't find a good Helms manual, I've tried that too. I figured someone on here could tell me what I'm missing. I've also studied faulty ICUs, but that doesn't seem to be part of my particular issue, and if it was, I can't find one of those anyway. So, if you don't wanna help, just scroll on by man.... electrical is not my strong suit. Forgive me I guess. The ECM is telling me the coolant temp sensor and AIT sensor is bad. Those are new and the ECM was purchased new old stock from California three years ago, and it produces the same codes as the original. I've read that the coolant temp sensor adjusts fuel trims, and that it causes a heat soak condition. Well....new sensor, third engine (I put the last one in myself), new ECM, same codes, same problem. So if I've missed a relay, or am putting the wrong ones in, it's because that's what I've found and....this is key....to my knowledge replaced. I've cleaned all grounds, I've looked on here for this problem and on the CRX enthusiast forum and not had any luck. Again, that's why I posted after years of reading and searching.

See what I mean? Two main relays, two different styles.

Tyson

For anyone else wanting to learn, the main relay is the large rectangular 7 pin box above the hood latch.

The partsgeek website is just wrong description for some other relay. I probably would never want to buy anything from them. But I can see why you're confused, sorta, except all the previous discussions and pictures are of the correct main relay, there should be no confusion.

You can verify parts from Honda parts sites. It correctly describes the main relay PN.

You can download CRX shop manuals. There's so many sources it not even worth linking.

Again, to fix a bad main relay, just resolder the joints.






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