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what’s up guys I’m new here and I’ve recently bought a 1988 Nissan sunny Ute. Since I’ve had it I’ve been trying to figure out why my engine wants to die when I have my headlights on. When I initially turn on the truck it will idle at about 1500 rpm and then find it’s way up to 2000 rpm as soon as I give it it one small rev the rpm will drop to 1000 rpm and maintain there. If I turn my headlights on nothing will happen but, if I rev it with the headlights on the rpm will drop to to 700 rpm. Does anyone know why this is happening and if so where I should start so I can fix my problem. I have replaced the OEM alternator with a 50 amp alternator. Thank you in advance!

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Sunny Ute? Is this an EFI engine??? They are very sensitive to low voltage. If not charging properly the headlights might draw just enough to disrupt the EFI.

 

Check the battery voltage with the engine running and when revved up. Should be just over 14 v.

 

What was the output of the original alternator? 

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1 hour ago, datzenmike said:

 

Sunny Ute? Is this an EFI engine??? They are very sensitive to low voltage. If not charging properly the headlights might draw just enough to disrupt the EFI.

 

Check the battery voltage with the engine running and when revved up. Should be just over 14 v.

 

What was the output of the original alternator? 

It’s a carburetor set up and yeah I need to find a voltage reader so I can see what it’s pushing and the original alternator was a 30 amp alternator. I was thinking the voltage regulators that the headlights are hooked up to might be bad and need replacing 

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I don't think the headlights have volt regulators but they may be on relays.

 

Here's what happened to me once with an old VW bug. Unknown to me the voltage regulator was not working but I was out long enough that it started getting dark so I had the headlights on. They were very dim and the engine was struggling. I shut them off to see if the lights were actually on they were so dim and the engine immediately ran stronger. Turn them on and the engine cut out. I was on back roads so I limped along with just the parking lights on and these became dimmer and dimmer and the last few miles I had the 4 ways on and made it home.

 

The ignition was running on less and less battery as it ran out. I suspect yours is doing the same.

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12 hours ago, datzenmike said:

I don't think the headlights have volt regulators but they may be on relays.

 

Here's what happened to me once with an old VW bug. Unknown to me the voltage regulator was not working but I was out long enough that it started getting dark so I had the headlights on. They were very dim and the engine was struggling. I shut them off to see if the lights were actually on they were so dim and the engine immediately ran stronger. Turn them on and the engine cut out. I was on back roads so I limped along with just the parking lights on and these became dimmer and dimmer and the last few miles I had the 4 ways on and made it home.

 

The ignition was running on less and less battery as it ran out. I suspect yours is doing the same.

I’ll have to take a look at mine then and I hope that’s the issue if so then it should be a very simple fix thank you!

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You say you replaced the original alternator, so...

 

 

Did this problem happen before you changed the alternator? or after??

 

Because...

 

If before then unlikely it's the alternator... unless a bad one was swapped in. Remote but possible I guess.

If after then likely the alternator. Or something was done during the installation to cause this, like leaving a wire off.

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 Does this '88 have a voltage regulator? Or is it built into the alternator?

 

Are the battery cables and posts clean and tight?

Does the red charge light come on when you first turn the ignition to ON before you start?

 

 

Then get some voltage numbers with it running and not.

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I put a Lester 14255 alternator which was a direct replacement. I replaced the OEM alternator because it was a 30 amp alternator and I wanted something with just a little more amps to it and this one is a 50 amp and is internally regulated everything I read on the OEM one said it was externally regulated 

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I put a Lester 14255 alternator which was a direct replacement. I replaced the OEM alternator because it was a 30 amp alternator and I wanted something with just a little more amps to it and this one is a 50 amp and is internally regulated everything I read on the OEM one said it was externally regulated 

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your repeating yourself.

Lester? Never heard of it.

like Mike said if one is internal and one is external then you have your awnser. if one is regulated and one not then the wireing don't match.

 

Put the externall alternator back in and adjust the carb and distributor to run when the lights are on.

 

a Suuuny ute I would think would be IR (internal regulated alternator) since build was 1988 but some of these were made in S Africa and still had point ignitions and maybe external volt reg alternators

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A little checking shows the Lester 14255 alternator as replacing the Hitachi LR150 making it an internally regulated alternator.

 

This is an A series engine? A B-210 is A series and 50 amp, between '75 and '77 were externally regulated. From '78 and on all N Am Datsuns were internally regulated.

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I live in Okinawa, Japan so yes a lot of the truck is pieced together from local parts and I can’t read kanji so I can’t get exact details on everything else so I’m sourcing parts from where I can so I know what’s going in now and thank you for the help I will go ahead and make the necessary changes and let y’all know the outcome. 

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I’m going to make the changes to the carburetor I haven’t had the time today but hopefully tomorrow the trucks OEM alternator was internally regulated so I don’t need to put the original alternator in there since the new one is also internally regulated and yes sorry I put Arizona cause I didn’t even think of it I just moved to Okinawa. Also I’m going to check all of my grounds again clean them and I just got a voltage reader so I’ll be checking the battery as well when I turn the head lights on and see if the volts are dropping too low

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23 hours ago, Anthonydat1200 said:

It has an external regulator the posts are clean and tight and the red charge light does turn on

 

56 minutes ago, Anthonydat1200 said:

I’m going to make the changes to the carburetor I haven’t had the time today but hopefully tomorrow the trucks OEM alternator was internally regulated so I don’t need to put the original alternator in there since the new one is also internally regulated and yes sorry I put Arizona cause I didn’t even think of it I just moved to Okinawa. Also I’m going to check all of my grounds again clean them and I just got a voltage reader so I’ll be checking the battery as well when I turn the head lights on and see if the volts are dropping too low

 

 

Conflicting information. If you gave these symptoms to  a doctor you might be dead by now.

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