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Old 09-26-2020, 07:50 PM   #1
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Default won't start, complex situation

Hey gang,

I looked thru the electrical section of the message board, but haven't found anything that looks quite like my situation. Hoping someone here can help...

So I have a 1988 D21 V-6 (sorta: it's actually a Sunrader RV on a D21 chassis). And it won't start. But here's the whole sob story, which I hope will lead someone to recognize the issue.

My buddy was driving it home from a trip, and about 30 minutes from home the dashboard lights went out. When he got home, he tried to start it again to move it forward a couple of inches but it wouldn't start. So it sat at his house for a couple of weeks before I could get over there to check it out.

When I came by I tested all the relays and they were fine. I found that each time I tried to start it, the 2 fuses in the upper right would burn out. One is marked "BACKUP / METER / LAMP" and the other is marked "AT CONT / SEAT HEATER / KICK DOWN." After burning out several 10A fuses, I discovered that I could get it started by "hotwiring" the BML fuse with a paper clip that I'd remove as soon as the engine was running, but then I'd have to drive with no lights on the dash and the fuel/temp gauges didn't work. Oh well, that was good enough for me to get it home.

On the way home I stopped for gas (bc I had no idea how much was in the tank since the gauge didn't work), and was able to restart it again, but then it wouldn't go above 25mph or so, and when it got home I couldn't get it to start again.

Now it's sitting in front of my house and it doesn't burn out fuses when I try to start it, but it doesn't start either.

One thing I discovered when I was looking at the wires by the fuse box is that there's a disconnected red wire which might go to a "thing" that someone on a Camaro forum identified as an aftermarket cruise control. But connecting that red wire to the loose wire on the "thing" doesn't help.

Anybody got any suggestions? I sure would appreciate it...
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Old 09-26-2020, 11:00 PM   #2
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Welcome to infamous Nissan! That’s a cool ass ride, I’d love to have one.

The two fuses in question feed a LOT of stuff. I’ve posted a link to the 1989 factory service manual below. My first general recommendation will be to make sure the fuse sockets themselves aren’t worn out. This can be a problem. Beyond that, there are just so many things it could be and I would look especially hard for any wiring modifications. People usually end up finding these issues by just digging around until they run across something abnormal.


https://www.nicoclub.com/service-man...truck_1989.pdf
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Old 09-27-2020, 12:23 AM   #3
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Quote:
Originally Posted by sweetleon View Post
My buddy was driving it home from a trip, and about 30 minutes from home the dashboard lights went out. When he got home, he tried to start it again to move it forward a couple of inches but it wouldn't start. So it sat at his house for a couple of weeks before I could get over there to check it out.
That's probably because the fuses were blown.

Quote:
Originally Posted by sweetleon View Post
When I came by I tested all the relays and they were fine. I found that each time I tried to start it, the 2 fuses in the upper right would burn out. One is marked "BACKUP / METER / LAMP" and the other is marked "AT CONT / SEAT HEATER / KICK DOWN." After burning out several 10A fuses, I discovered that I could get it started by "hotwiring" the BML fuse with a paper clip that I'd remove as soon as the engine was running, but then I'd have to drive with no lights on the dash and the fuel/temp gauges didn't work. Oh well, that was good enough for me to get it home.
What else is supposed to turn on when the Backup Lights come on? I mean, you are driving an RV. Is there a Backup Alarm or some extra lights that you added?

If you spend time looking at how Nissan runs the wiring for the lights, they are HOT, meaning that they have power all the way out. All the switches do is provide a source to ground to make the connection. So anything added by a splice (like a backup alarm or trailer wiring harness) can cause the fuse to blow if the wiring ever comes loose.

That red wire? Find out where it goes. Up under the dash or under the carpet? Well, it comes out somewhere. You are going to have to find it because that wire isn't anywhere in the Service Manuals. You need to find out what that wire goes to, if it is tied to something that has power, and if it is grounding out somewhere.

The ECU is responsible for making sure the vehicle doesn't crank when it is in gear, including Reverse.

That's what I think is going on. Finding it will just take time.
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Old 09-27-2020, 02:06 AM   #4
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My 2 cents worth on the fuses. My truck blows the back up lamp fuse when a trailer is connected and the reverse lights go on. Somewhere there is a short that I can't find. You may have something going on like that too. Unfortunately you don't have the luxury of just unplugging a trailer before backing up.



Your ECM is likely in limp mode. Is it an automatic? PCM might be in a limp mode if it won't get you go too fast. Generally limp mode is 2500RPM.
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Old 09-27-2020, 05:54 AM   #5
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Thanks! It is an automatic and it had something hooked up to the reverse lights (a backup camera) which I removed as soon as I realized the fuse was blowing.

I’ll give it a shot next weekend with the ECU and tracking down that wire.
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Old 09-27-2020, 11:15 AM   #6
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The tail lamp/tag light harness can be unplugged. The connection is on/near the frame in the general right rear wheel area. If you can find that, unplug that section and see if the fuse still blows. If that does happen to be the trouble area, that would narrow the problem to either the tail lights, brake lights, turn signals, or reverse lights.
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Old 09-27-2020, 11:39 AM   #7
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The tail lamp/tag light harness can be unplugged. The connection is on/near the frame in the general right rear wheel area. If you can find that, unplug that section and see if the fuse still blows. If that does happen to be the trouble area, that would narrow the problem to either the tail lights, brake lights, turn signals, or reverse lights.
Good idea!
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