I just installed a new opti and the car doesn't start. The car has spark but no fuel. When you turn the car to on you can hear the fuel pump prime. And if I bridge the fuel relay so the pcm has nothing to do with it the car runs fine. If the PCM does not receive the low resolution pulse from the Opti the PCM shuts off the fuel pump, and creates a generic ignition timing. I am convinced that this is the problem. Is their anyway to check the signal from the opti to the PCM? thanks in advance.

 

The most accurate way to test either of the resolution signals is with an Oscilloscope. The service manual says to use a DVM and check to see that they are 5 volts. However, since the signal is essentially a square wave from 1 to 5 volts, when the engine is rotating. If the signal is low when you check it, it may not read 5 volts.

 

If there is no low resolution pulse, your engine would not even run, so that is not the problem. There is no "generic timing". You said you had spark, so the opti is working.

Did you test at the relay to see if it is working or getting a signal to turn on? Sounds like that is where you need to be checking.

 

I replaced the relay, and it had the same result. correct me if I'm wrong but everytime you turn the key on the fuel pump will prime. It will run for 2 seconds, and if the engine is not running then it shuts down. The PCM will also shut the fuel pump and injectors down if the PCM cannot find the low resolution pulse pattern from the opti.

Odly enough I do have an Oscilloscope, but what is a DVM?


Thanks for your help.

 

DVM is digital volt meter. You are correct in that the PCM will kill the relay if it does not see the pulse after 2 seconds of cranking.

Let's take what Shoe said and go with that for the moment. Let's suppose the that the voltage to pull the relay in were not present. But instead of the opti signal being the reason, it is because of a bad wire. Changing the relay would not fix this problem. In other words, you think the output is stopped because of input to the PCM but it may just be an output problem. If what Rob says is correct, than check the socket to see if the relay coil is being powered up, which it apparently isn't. Then check the output from the PCM to see if it isn't getting to the relay socket.

What is curious is you only changed the Opti and nothing else. Do you perhaps have a bad wire between the opti and PCM? Why did you replace the distributor? Were you having a problem that the opti replacement did not cure?

Check all the connectors for bent pins and pull the insulation back at the pins and look for corroded connections. Also ohm out all the wires from end to end to see that you have continuity. If they are all good, put di-electric grease on the connectors before you plug them back in. BTW, unplug the wires at both ends before you ohm them out to avoid possible damage to any sensitive components since ohm meters put out voltage.

 

I apologize that I skipped over part of what you originally said. I was kinda tired last night.

It does sound odd that you can hear the pump prime, but it does not seem to run when the engine is cranking. I would use a meter and try to monitor the wire from the pcm to the relay to see what it is doing. You could even have a pcm problem (rare, but possible).

 

I'll try that and see what happens, would a pcm problem trun on the SES light, when I jump the fuel relay ( so the PCM has no influence) it's not on. Thanks for helping out shoebox.

 

I doubt that you would see any SES from your problem.

 

Since the Opti low res pulse is at a rate of 4 pulses per crank revolution (8 per cam revolution), couldn't you check for output with a frequency counter, sometimes found on a digital multi-meter? At 500rpm crank speed, you would expect to see 2,000 Hz, for example.

Just a thought.

 

Good point Fred, never thought about a DVM with frequency but I wonder what voltage they work with. I keep thinking they had more to do with AC voltage then a square wave. Not sure if that would work if that's the case since a square wave goes from 0 to a positive voltage and AC goes from a positive to and equal negative voltage but a damn smart thought none the less. I'm impressed.

 

Opti is working fine. I put the fuel pump relay back in to double check and the fuel pump isn't priming (hmm... I could have sworn it was) I have checked all the wires and is far as I can tell the wire from the PCM (green w/ white strip) is not carrying any voltage, a faulty PCM crossed my mind but is their a way to check it.

 

What I would do is check the continuity of that drk grn/wht wire from the pcm to the relay. Unplug it from the pcm and check it with a meter by looking at ohms end to end or by grounding one end and looking at it with ohmmeter to ground on the other end. If you see no problem with it, look real closely at the pins and connector at the pcm.

Remember, when it is all connected up, that you will only see voltage on it for 2 seconds when you first turn the key on.

 

Man do i feel sorry for you! my car has been down for 3 weeks cause of no spark. i changed the opti 2 times, the pcm, the icm, and coil, and checked wires for continuity! and my car will still not start! i still do not know what the problem is. i have now givin up and am taking it to the shop tomarrow! but listen to slopokrodrigez, he know's his stuff! good luck, and thanks for the help w/ my car dave! its to bad it has not started, but i really thank you for the help you offered! I will let everyone know what the problem turns out to be w/ my car, that is if the shop can figure it out!

 

I just want to chime in with StrkdFormula383, thanks guys, you have no idea how thankful I am for helping the people out on this board.

 

You might want to save the accolades for when you find and fix your problem.