My Datsun truck wont rev up

[Datsun1]

My 1978 Datsun truck has had timing fixed new distributor and plugs and plug wires it wont rev up just idles thought it was the transistor box because when unplug the fusiable link it runs perfect but if you mess with the lights and stuff it either kills it or makes it just idle the alternator is good I just can't figure it out plz help

[datzenmike]

Run on sentence is hard to understand and can cause confusion in answers. Take the time to use proper punctuation... it saves time in the long run.

 

 

What fusible link? There is only one, and everything is run through it. If you unplug it, everything shuts off.

Mess with lights? Turn them on???? Lights on shuts off or lights on it runs?

 

Get a volt meter or borrow one.

Engine off measure across battery posts.... should be around 12.6v if battery charged.

Engine running.... about 14.6v

 

Has the alternator been replaced?

[Datsun1]

The fusiable link on the hot wire. Its the little wire that runs to the hot post on the battery. When you unplug it the truck will run perfect. If you have it unplugged and mess with the lights or other things in the dash, it'll either kill the motor or make it only idle. Leaving it unplugged the truck wont start back. I thought the alternator was shorting out but it's good. It has had a new distributor, timing chain Spark Plugs and plug wires. Also tried another transistor ignition box it didnt help

[datzenmike]

There were two alternator styles used on the 620, those before '78 used an external regulator, '78 and '79 had an internal regulator. It may have the wrong one.

 

Try unplugging the alternator, the little two wire plug. This will remove it from the electrical system. See if that changes the problem.

[Datsun1]

What do you mean an external regulator. That's inside the alternator? Or somewhere on the truck elsewhere?

[datzenmike]

'77 and earlier trucks had an external regulator mounted on the inner fender behind the battery. '78 and '79 did not have them as the regulator is built into the alternator. If you accidentally have an earlier alternator it won't run right. Unplugging it simply removes it from the electrical system... if it starts running right then this may be the problem. Naturally it won't be charging and the charge light may come on. It doesn't fix the problem only point to a possible cause.

 

Was your alternator replaced?

[Datsun1]

To my knowledge no. it may have been years ago, but recently no

[Datsun1]

If that regulator goes bad will it cause it?

[datzenmike]

Don't know. If the regulator packs it in it just stops charging usually.  Unplug it. See if anything changes.

 

 So... has this truck ever run properly? is this a new problem that just started? If it run perfectly and this problem just started it tells me that you probably have the correct alternator and the wiring is fine. If you just got this truck then a lot of questions need to be asked and answered.

[Datsun1]

My dad has had the truck since the 90s. He drove it til probably around 2013. It got the problem that it didnt want to start and to get it to start you had to file the rotary in the distributor. Well he put a new distributor, timing chain, Plugs, plug wires in it and it only idles. when you push the gas pedal it backfires and wont rev up. It kindly acts like a lawn mower with bad gas. So he parked it. Well he handed it to me and ive figured out that if you take the fusiable link off of it it'll rev up and is drivable, but if you mess with any knobs or turning signals in the truck it'll either,kill the motor or take it back to just idling. My dad thought the distributor was not right because it isnt,new. where I am from its hard to,get parts and he had it sent off and fixed. I hope you can help,me because I really would like to get this,truck back on the road 

[Charlie69]

If it is a 78 it should have an internal regulated alternator.  Mike what happens if you install an alternator that is not internally regulated in a truck that is supposed to have an internally regulated Alternator?

Edited August 17, 2018 by Charlie69

[nl320what]

48 minutes ago, Datsun1 said:

My dad has had the truck since the 90s. He drove it til probably around 2013. It got the problem that it didnt want to start and to get it to start you had to file the rotary in the distributor. Well he put a new distributor, timing chain, Plugs, plug wires in it and it only idles. when you push the gas pedal it backfires and wont rev up. It kindly acts like a lawn mower with bad gas. So he parked it. Well he handed it to me and ive figured out that if you take the fusiable link off of it it'll rev up and is drivable, but if you mess with any knobs or turning signals in the truck it'll either,kill the motor or take it back to just idling. My dad thought the distributor was not right because it isnt,new. where I am from its hard to,get parts and he had it sent off and fixed. I hope you can help,me because I really would like to get this,truck back on the road 

Must grab and meter as it sounds like wires are crossed and its dropping the 12VDC to the ignition coil to half or less.

 

I would just go around with the meter and check lighting voltages and things with the bulb connectors disconnected and try the switch in varous positions and track down your issue.

 

Go through it all and trace wiring with a diagram is needed.

[wayno]

First thing I would ask is who did the timing chain replacement?

Does it rev up slow or fast when it does rev?

 

What sounds like he is saying is that when he removes power to the fuse box the truck runs good but once it is shut off it will not start again which makes sense to me.

First thing I would do is isolate the alternator from the loop/system, start it and see what happens.

 

[Datsun1]

It has never had an altenator put on it and I'm gonna try and check my,wiring. Yes it does rev up fast

[Stoffregen Motorsports]

Not revving? Alternator?

 

I think I would look at other areas like cam timing and distributor timing and function.

[Datsun1]

It has something to do with the fusiable link and the dash. The alternator is fine. We took the fusiable link loose and itll rev up and everything. If you do turning signals it'll start to just idles . hazard lights it just idles and lights it dies. Thats with the fusiable link disconnected. What does the fusiable link do and where does it go ive run it down to the fire wall

[datzenmike]

 

 

The fusible link brings power to the ignition switch and the fuse box but in the event of an accident where the wire is pinched, it will melt and break the connection (just like a fuse) but not catch fire. The fusible link (or in some cases links) carries all electrical loads except the starter.

 

 

If you have an EI distributor the electronics are very sensitive to low voltage.

[Datsun1]

It is a Electronic distributor my fuses are good i checked those. My column is loose and wigly, could my switch short it out

[datzenmike]

There are two style EI distributors and on top of that, cheap ass $100 Chinese knock offs.

 

 

If it idles when the lights are on then it still works but if the voltage to it is lower the output will be also. It takes less spark to idle that when revving up. Get a meter and see what numbers you are getting between the battery positive and ground...

 

engine off.

engine on

engine on and headlights on

 

Now try the same but between the coil positive terminal and ground.

engine off.

engine on

engine on and headlights on

[Datsun1]

Ok I'll do this tomorrow and get back to you all my distributor might not have been fixed right because it is the one that came on it it was just rebuilt

[datzenmike]

So not a new one.... can you also look for the part number on the side of the distributor?? 10 numbers starting 22100-?????.

 

 

Seems odd that disconnecting the fusible link makes it run right or turning the lights on doesn't. Has to be electrical.

[Datsun1]

Yes I'll get the part number. Where is a good place to get parts. With the lights, its when the fusiable link is disconnected it kills the motor. When the fusiable link is disconnected it sounds like the motor speeds up

[Datsun1]

The number is 22100- 89800

[Rays74]

On 8/18/2018 at 2:20 PM, Datsun1 said:

The number is 22100- 89800

All of the Nissan distributors I've seen have a letter in the part number stamp....look again ?

[datzenmike]

On 8/18/2018 at 2:20 PM, Datsun1 said:

The number is 22100- 89800

 

 22100-B9800 (looks like an 8 )   August '77 to June '78 (making it a '78 model year) 620 manual trucks Federal Emissions and also for Camper. This would be a remote igniter EI with the box under the dash