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I have been given a 1990 Nissan Maxima with 137000 miles that will not start. I am trying to isolate the problem and would appreciate the help of any and all. I am a fairly ignorant, but adventuresome novice. My experience with cars is mainly keeping my 1985 Toyaota Camry (249000 miles) running. I am pretty good at repair, but troubleshooting is not my strong point.

It's an SE--VG30E SOHC V6, manual transmission.

This is what I know:

The car had been running fine. It died abruptly and has not been started since.

The starter cranks the engine fine, but there is no firing whatsoever.

The person from whom I received the car suspected that there was no ignition, and checked out a number of things prior to giving it to me, but at the time said he suspected the ECU.

Since I have had the car I have done the following:

1. I have tried to read the codes on the ECU, but cannot get any lights at all. I tried to follow the procedure to put it into Mode 3, but I get no flashing lights at all.

2. I listened for both fuel pump and injectors with the ignition turned on and can hear nothing. I ohmed the fuel pump relay and it seemed OK.

3. I followed Diagnostic Procedure 22-Main power supply and ground circuit on p. 4-51 of the Chilton manual with following results:
(A) voltage between ECU harness terminal 16 and ground is supposed to yield 1 V--I got 12V.

(B) voltage between terminals 49/59 and ground is supposed to read 12V, but I got nothing.

(C) the harness continuity between the SMJ (does anyone know what SMJ stands for?) connector and the battery was OK.

(C) I checked the ECCS relay--both by ohming the lugs and by applying voltage to make sure it worked. It was fine. I checked the fusible link, which was also fine. The book then says to check out joint connectors E50 & E52, but I have been unable to locate either.

My questions:

Am I barking up the wrong tree here? Is there another, perhaps more likely problem?

Does the ECU control the fuel pump, injectors, etc.; is it possible that the fuel pump not running is attributable to the ECU malfunctioning?

If I get no lights at all at the ECU, does that necessarily mean that it is bad? Is there another way to test the ECU?

Any other suggestions?

Thanks, I would really appreciate any help you could give.
 

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I had i similar problem with my 89 se and it turned out being that snout on the crankshaft had broken, and although the crankshaft pulley turned a little bit, it was not attached like it was, and wouldn't fire the cylinders up. I replaced nearly everything before my grandfather talked to an import mechanic and he told him about a common problem with them. This is just a suggestion though, it could be something else. Good luck.
 

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Hmmm...Did you check the fuel pressure? Also you said it is a manual right? Does the clutch need to be engaged before the engine will turn over? Maybe the sensor for the clutch pedal can't tell that the pedel is engaged. Just a guess.

old90
 

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First and foremost... TIMING BELT.
pull the distributor cap off and crank the engine. does the rotor turn?
If not, then the timing belt is broken. throw the engine away. (interference engine, and I guarantee it bent at least a few valves.)

If it does turn, then you've got lots of other places to look. but check the timing belt first- it'll take a whole 30 seconds.
 

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old90 said:
Hmmm...Did you check the fuel pressure? Also you said it is a manual right? Does the clutch need to be engaged before the engine will turn over? Maybe the sensor for the clutch pedal can't tell that the pedel is engaged. Just a guess.

old90
The engine wouldn't crank at all if the clutch wasn't engaged. It's not a sensor, it's like a button that the actual pedal pushes down at the furthest point in its travel. So do what matt said and go from there, i could probably hook you up with an engine for 150 or so if the engine is gone. Good luck
 

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Discussion Starter #6
an update and more questions

OK--I've tried several things:

It's not the timing belt. Cranking the engine definitely turns the rotor.

I cannot hear the injectors clicking when the engine is turned. Granted, I don't exactly know what I'm listening for, but I don't hear anything other than the noise of the starter turning the engine.

At this point, I'm willing to assume that it is the ECU, but I have several questions.

1. I am not getting 12V to the ECU where the Chilton book says I'm supposed to. I checked the voltage between the terminals on the harness connector (the female side of the connector) and ground, and got the results mentioned above. The procedure is not very clear in the book. It says that if this step is no good, then check the harness continuity between the ECU and the battery, which I did and it was OK. So far everything I have checked in steps 2 & 3 have checked out OK. So, what could be the problem that I am seeing when I check the voltage to the ECU?

2. Someone on another forum mentioned that "It is known that heater core leak will fry the ECU." Pardon my ignorance, but what is heater core leak. The heater core is the main heater unit under the dash? How and what does it leak? If mine leaks, and I put a new ECU in, I presume it will destroy the new one as well?

3. If I get an ECU from the junkyard, can I know for certain that it is good? Is this a good risk? Would I be better of to buy a refurb unit (which I have heard you can get for <$300) on the understanding that it is known good and will not fail prematurely?

4. How do I make certain I get the right ECU? Can a Nissan dealer match the VIN to the correct model ECU?

Thanks to all for your excellent help.
 
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