Symptom: Hot start fail. Result: replaced FP regulator, pump relay, Radio Noise relay, RPM sensor, cleaned IAP and throttle body. Remaining issue: No fuel pressure w/ fuel odor, but no visible fuel leak. Question: Would I smell fuel if injector(s) is/are dripping fuel internally? I have not pulled rail/injectors yet. Where else could the leak be coming from?

 

I suppose it could be injectors leaking. It also sounds like you could be having a couple of problems at once.

A vacuum leak would cause hard starts when hot, the same leak might not be noticeable when starting a cold engine because on a cold start the computer runs the engine rich for a few minutes.

One of the safety things about this engine is if the computer senses a no spark situation, it shuts off power to the fuel pumps, so it is possible that you are losing spark when hot. Which should be your next test when it fails to start, look for spark. There is a power to the coil test lead at the back of the head, it is a white/red single female wire, a voltmeter there and ground should be battery voltage, do that with the ignition on, engine not running.

Also your fuel pressure, when measuring it, when it will not start, does it initially go to pressure when the ignition key is turned to "on" but not to start? There should be an initial charge of fuel once the key is turned to on, then the pumps shut off until the engine is running.

There is also an ignition relay that is on the front fender driver side, it is identical to the injector relay, same part numbers, try swapping them and see if things change.

One thing I have to do on my '94 is, every year clean and tighten all under hood connections, especially the big 50+ pin connector on the shock tower.

Get back to us, this should be an easy one.

DanR '94 964 360,000 miles (126,000 on the new engine)

 

No HOT start, hmmmmmmmmmm, that means that the fuel pump is working since it starts fine cold. Since you already replaced the FP realy, I assume that is fine.

When starting cold, the motor gets more air and runs rich, my guess is that you either are NOT getting enough air due to a vacuum leak or you're getting to much air.

Just to confirm, you can hear the fuel pump whine up and down while cranking (and a few seconds after), correct?

If you smell fuel, you likely have a vacuum leak which could be taking away needed air.

@Dan, is there a temp sensor that has to work properly to get a hot start?

 

I hear the pre-pump buzzing, when removing the gas cap after cranking, but not the whine up/down when cranking. That might be the problem after all.

 

Well, I don't mean the pre-pump, I'm more concerned about the main fuel pump. It will come one while cranking but you won't be able to hear it. When you release the starter/ignition, if the car fails to start the pump should run for about 3 seconds then cut off. That's the sound I'm looking for.

 

it was the temp sensor below the RPM sensor; after replacing the RPM sensor, i punted and let my volvo mechanic friend climb back down there to replace the temp sensor; he checked fuel pump-ok; fuel pressure-ok. On to new codes...