I know, I know, search search search. I gleaned as much info off the forums as I could before starting another "no start" thread. Learned a lot. But still the problem lingers!

The situation:
89' 740Turbo SOHC, randomly won't start. I know it is fuel. I can put a vacuum line into a can of fuel and it fires right up. Because of this fourm: I have checked the fuel pump each time to ensure I still have fuel and I do; I replaced the impulse sensor in the distributor thinking I had it. But three days(afterstarting just fine)later it leaves me dead again.

It does the same as others describe. Won't start once at random but then will again the next time (or many next times) at random.

So my question is what else relates to randomness? Everyone tells me the ECU doesn't fail randomly. The O2, or coolant temp shouldn't cut off fuel, only meter it poorly (if failing). So what else is random? Today I am going to change the FPR, I don't smell fuel but I feel it is worth a try.
Does MAF, TPSfail randomly -and cause ano fuel output condition-when they are?

I will be sure to list the final solution for the search records. In the meantime any thoughts? cause I am out of options.

 

Have you checked one of the most important things in the system the fuel pump relay?

What is the date stamped on the side of it?

 

Hi Tech

I didn't check the relay because I can confirm the pump is running. It was so loud that wasn't a problem to hear it running.
I just finished replacing the FPR and the in line pump and still it happened again.

I don't know what the number on the rely is. Is it important? What does the number mean? The relays are way up under the
ash tray in the center console, I'm not sure of an easy way to check them. Can I pull the entire relay tray out like I do on my VWs?

Oh I also checked to be sure the injectors were pulsing as well. The ol' LED in the plug test and they each fire rapidly.

I'm out of ideas. It keeps dumping my daughter in the worst places.

 

Originally I asked about the relay because it controls the pump and injector pulse as well.
But you confirmed the pulse.

The Date is stamped on the side. They usually last about 5 years.

You can pull the little cubby out and get right to the relay. Just pull the relay out.

Next time it won't start unplug the mass flow and see if it starts if it does the mass flow is bad.

Also how many black relays are under the hood by the coolant bottle?

 

Alright, I'll check the MAF, I think it is stalled and in a parking lot again.

I'll check the relays as well, I don't remember off hand.

Damn your fast on the responses, I won't be able to check these things until after work tomarrow but I'll be sure
to report regardless of the outcome.

It sucks because everytime I think I have it solved I can't really be sure because it is random and will start fine for 10-20 times.

Oh, and the CEL isn't on either. Where would thecheck box be on this model if the CEL was on? I thought it was under the hood behind the drivers strut tower but I can't find anything that looks like it.

 

Checked the MAF this morning. Unplugged and still no start.
Relays by the overflow tank? Zero

There is a relay by the PS tank on the drivers side fender but none on the
passenger fender.
What is the significance of the relays?

What else might I try?

 

I went back over all the past posts of others problems. Tech your talking about the RF suppressor relay near the coolant tank. I didn't see anything near the coolant overflow tank but there are four big ceramic looking ballast resistors next to the radiator (intercooler) on the drivers side. It is up in the core support area though, right behind the drivers side headlight bucket. I don't remember seeing a relay but there may have been, I can check. I don't exactly see how this would relate to fuel delivery though?

If I know the injectors are pulsing, and I know I have fuel flowing, and I have a new pump and FPR, how it the fuel (even randomly) not making it into the combustion chamber? The only thing I don't know for certain is the psi of the fuel in the rail. Do injectors have to have a minimum pressure behind them before opening? Even if that is the case replacing the pump and FPR should have solved that.

 

The relays I was asking about one also controls all the fuel and injectors as well as the white fuel pump relay.

Are the plugs really wet?

Maybe the injectors are sticking open and flooding out the engine.

 

I thought of that when this problem started. I haven't ever smelled gas from the exhaust, I stopped checking though.
No I haven't pulled the plugs. Iamquite sure it is not flooding but at this point I'll try anything. Wouldn't flooding (upon
startup) be caused by a faulty coolant temp switch?I haven't checked that yet but it was next on the list.

 

Yes it could be.
Or a bad cold start valve if your car has one.

 

I can't seem to find a socket that fits the plugs. I hate working on cars in other peoples driveways

So I tried one of the first things again just to confirm the flooding you were thinking it was. But I am sure it is lack of fuel.
I put a vacuum tube into a can of fuel and it firesupjust fine. Of course only as long as I leave the tube in the fuel.

 

The spark plugs should be a 13/16.
The maybe a weak fuel pump.
Try cycling the key about 5 times or so and see if it starts easier.

 

Eureka!!! A faulty ignition switch was to blame. I kept ruling it out because wiggling and twisting it violently didn't seem to
help any.

Too bad I couldn't figure it out, I had to take it to a mechanic. But at least this a another in the log book of things to check for.

 

Change the white (fuel pump) RELAY!!!