# 94 Maxima DOHC



## Tommy Allen (Mar 4, 2005)

I am in the process of retrofitting my 94 Maxima. It had 260,000 miles and the engine was sounding funky. I was driving down the interstate and it stopped running. Just as if you turned the switch off. After evaluation, I decided that I wanted to retrofit. Interior is perfect, all leather and I really liked and enjoyed driving the auto. Plus some seminital values. I started the project. Looked at rebuilt engines from several sources. Finally decided to order a replacement from a auto salvage. It was out of a 94 SE with 43,000 miles. When it arrived the old wiring harness was still intact throughout the engine and cut where it leaves the engine and enter the auto interior. It was the same harness that existed on my engine. One exception the replacement engine was was for a auto with a manual transmission. Mine is a automatic. All harness connections matched except for a connector in the rear of the engine that I assume was a connection for the manual transmission control. After inspection that connection on my existing wiring harness it had a dummy termination on the harness that look to go to that connection. All other connections matched perfectly. Even to the color codes of the connectors. The replacement has been installed and in place. I am sure that all connections are terminated properly. I replaced the CV axles, struts and lower ball joints. new radiator and power sterring pump. The alternator and starter was taken to Southern Armature here in Birmingham and was rebuilt and reinstalled.

Now to the problem.

After reinstallation the engine would turn over but will not fire. Not a sputter. I have checked the fuel down to the porportional control valve and fuel is present. I do not know if it is getting through the injectors to the cylinders. I haven't got the test node necessary to check the injectors. It is my understand that the fuel pump could still be the problem. The existing pump may pump fuel but with not enough pressure to force it through the injectors. My next step is to replace the fuel pump, which I was going to do anyway as the existing has 260,000 miles.

I seem to have a electrical problem. I orderd and reinstalled a rebuilt computer from a company in Florida. It was a HW and the numbers matched up perfectly. So I am sure it is the proper repalcement. 

The engine would still not fire at all. I Started troubleshooting the electrical which is a problem. I have a Hanes maual and the electrical circuit diagram is not accurate. All fuses and fusible links were tested and are OK.I placed one of the original spark plug coils with a spark tester in place and checked for fire. It was sparking. On a second test after several trouble shooting I reconnected the tester and it did not seem to be sparking. The diagram That I have shows that the spark and injector power is from the same circuit. I then taped into the + side of the power circuit that supplies the spark plugs. I then showed a spark. I assume it backfed to all coils and also the injectors. prior to this time I was checking the anti theft system. The relay and fuses. 
The fuses were good. But I was getting 12.5 volts on both sides of the anti-theft relay coil. I assume that could be part of the problem. With the relay removed. I would think that only one side of the coil should be hot and the other side of the relay should have no voltage at all. I am really thinking that the anti-theft system could be shutting down the system and that is why I was showing voltage on both sides of the relay with.

I guess my questions are. 
1. Does anyone have any suggestions.
2. After doing all this work and to solve this problem. I probably need a set 
accurate manuals with the proper wiring diagrams for this wiring harness.
Does anyone have any suggestions as to here I can get the best and 
most accurate manuals for this precise model.

Thanks,
Tommy


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## Matt93SE (Sep 17, 2003)

www.phatg20.net for the manual.. sign up for an account and go to their download section. you can get a copy of the nissan service manual on .pdf there.

as for the problems with the engine, it sounds like it could be one of many things.. since the original engine just died while driving down the road, it could be something related to that problem and nothing to do with the engine itself. (i.e. fuel pump)

the other common issue is the ignitor chip, or power transistor unit. they're common to fail.. replace it with the one off your old engine and see if it works..

Was the engine a JDM engine, or US-spec engine? There are a couple of sensors that you need to replace when installing a JDM engine. the coolant temp sensor, and a couple other small ones that you can just swap over from your old engine.. I forget which ones now..


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## Tommy Allen (Mar 4, 2005)

*Thanks for the reply*

Thanks for the information. It was very informative. I did not realize that the manuals were available by signing up for an account. That makes it easy and quick. I did switch the power transitor unit. The replacement engine was a U.S. engine. I am thinking about disconnecting from the computer and utilizing a tone generator to trace the engine control circuit. Do you see any problems that may create?



Matt93SE said:


> www.phatg20.net for the manual.. sign up for an account and go to their download section. you can get a copy of the nissan service manual on .pdf there.
> 
> as for the problems with the engine, it sounds like it could be one of many things.. since the original engine just died while driving down the road, it could be something related to that problem and nothing to do with the engine itself. (i.e. fuel pump)
> 
> ...


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## Matt93SE (Sep 17, 2003)

I don't see any issues with that, no..

first I'd check the fuel pump though and see how much pressure you're getting at the injectors.

Is there a reason you swapped out ECUs when you did the engine swap? Make sure all of the wiring on the ECU is plugged in properly- don't just use the screw in the middle of the connector to force it in.. make sure you push the edges in as well.


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## Tommy Allen (Mar 4, 2005)

Good morning,
I will check the fuel pressure. I was going to install a new fuel pump as part of the retrofit.Simply because the existing has 260,000 miles. 
As to the question of the new ECU. I had convinced myself that was the problem. 
Thanks for the information. You have been a great help. it is always good to be able to bounce ideals as well as recieve good advice.
Tommy


Matt93SE said:


> I don't see any issues with that, no..
> 
> first I'd check the fuel pump though and see how much pressure you're getting at the injectors.
> 
> Is there a reason you swapped out ECUs when you did the engine swap? Make sure all of the wiring on the ECU is plugged in properly- don't just use the screw in the middle of the connector to force it in.. make sure you push the edges in as well.


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## Matt93SE (Sep 17, 2003)

Great.. good luck with everything.. try pulling the connector out of the ECU and reinstalling it. turn the screw a bit, then push the connector in by hand.. turn some.. push.. turn. push..
will take a whole 5 minutes and you'll know it was seated properly.

also check all fuses goign to the ECU if you haven't already. (think I said you did.) even with the ECU dead, the starter will still turn and crank the engine, but the ECU won't fire the rest of the system up...

good luck!


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## Tommy Allen (Mar 4, 2005)

*Thanks*

Thanks for the help. I will let you know how it turns out and what I find as the problem.
Tommy


Matt93SE said:


> Great.. good luck with everything.. try pulling the connector out of the ECU and reinstalling it. turn the screw a bit, then push the connector in by hand.. turn some.. push.. turn. push..
> will take a whole 5 minutes and you'll know it was seated properly.
> 
> also check all fuses goign to the ECU if you haven't already. (think I said you did.) even with the ECU dead, the starter will still turn and crank the engine, but the ECU won't fire the rest of the system up...
> ...


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