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1984 Nissan/Datsun 2.4 Truck will not start. Please Help!


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#1 84 Nissan/Datsun Truck

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Posted 06 October 2011 - 06:13 AM

I recently purchased a 1984 Nissan/Datsun truck and I drove it home with no problems. 2-3 days later I began cleaning and repairing floor rust and when I tried to start the truck, it would not start. So far, I have checked the fuses, I replaced the battery, fuel filter, fuel pump relay inside the cab under the firewall on the passenger side and the fuel pump. I also relpaced the air filter. My brother In-Law checked to see if I was getting power to the fuse box and he determined yes. But, the fuel pump does not seem to be getting any power. The only way I can start it for a short period of time is when I uses starter fluid. Thanks for your time and responses.

John.

#2 datzenmike

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Posted 06 October 2011 - 06:45 AM

First, never trust any fuse on looks alone even the plastic ones used on the 720. Replace it or swap with an equal value one. I'm at work and can't get to my circuit diagram right mow but will when get home tonight.

The pump relay is like the interior lamp delay, it allows the pump to start but times out and tries to shut off. During the run time alternator output and oil pressure inputs hold the relay in the on position. The timer/relays are notorious for the solder to break at a joint and leave you stranded.

#3 Sealik

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Posted 06 October 2011 - 07:02 AM

The timer/relays are notorious for the solder to break at a joint and leave you stranded.


Yup...just had that issue...which did leave me stranded... :D
I knew what it was....but said fuck it and got a free tow home instead.
Key on...should hear the pump for about 5 secs.
Give the relay/timer a shake or whack with a screwdriver...temp fix though
Junk yard...short phillips screwdriver...fill pockets :)

#4 datzenmike

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Posted 06 October 2011 - 09:24 AM

He said he replaced it but it wouldn't be the first time thre was a bad one in the box. There's a great little write-up about fixing thm. See if I can find it.

#5 Sealik

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Posted 06 October 2011 - 09:39 AM

He said he replaced it but it wouldn't be the first time thre was a bad one in the box. There's a great little write-up about fixing thm. See if I can find it.



Yeah...I was thinking of the timer...where the relay plus into.
I changed my relay after it died....worked good for a few days, then it calved again.
Guess I worked something loose in the timer while changing the relay the first time...changed the timer....good to go.

#6 datzenmike

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Posted 06 October 2011 - 06:54 PM

I recently purchased a 1984 Nissan/Datsun truck and I drove it home with no problems. 2-3 days later I began cleaning and repairing floor rust and when I tried to start the truck, it would not start. So far, I have checked the fuses, I replaced the battery, fuel filter, fuel pump relay inside the cab under the firewall on the passenger side and the fuel pump. I also relpaced the air filter. My brother In-Law checked to see if I was getting power to the fuse box and he determined yes. But, the fuel pump does not seem to be getting any power. The only way I can start it for a short period of time is when I uses starter fluid. Thanks for your time and responses.

John.



Found it.......

______________________________________________________________________________________

Who This Pertains To
This article is written for owners of the 1981 to 1985 Datsun or Nissan 720 pickups with the electric fuel pump. If like me, you have trusted in your Haynes© manual to troubleshoot a fuel delivery problem, you may have found that nothing works. You’ve checked the fuse (Fuse #2) and it’s good! You’ve checked the output of your electric fuel pump (just in front of the passenger side rear tire) – it works most of the time, or maybe only if you power the pump with a jumper wire! Yet, your pump just won’t put fuel to the carburetor when it’s supposed to… or it will for awhile – then the truck dies and leaves you stranded for 10-15 minutes – or until tomorrow?

It is likely that the trouble lies in your fuel pump relay. Now I know – the “book” doesn’t say ANYTHING about a fuel pump relay and many mechanics don’t even know about it (they’re probably using the same book). However, there is a fuel pump relay – or more precisely, a fuel shutoff relay. In fact, the Auto Choke Relay is mounted on the fuel pump relay. Trust me, it really exists (don’t believe Chapter 13, figure 5.2b). I have a 1981 Datsun and a 1984 Nissan and they both have this troublesome black box. Your repair guide not only ignores it, but it is conspicuously absent from the wiring diagrams, making diagnosing and repairing electric fuel pump problems virtually impossible. I tore apart my wiring harness to discover it – before I found that other shade-tree mechanics were discussing it in online forums.


Look Under Here!
Posted Image See all 5 photos
Where Is It and How Do I Get It Out
To find it, look under the dash on the passenger’s side. It is just visible above the kick panel in front of the door and will have the Auto Choke Relay attached to it – and in automatic trucks, the Fuel Cut Solenoid.


Look Closer
Posted Image The fuel pump relay itself has a 6-pin connecter going into it – those are six wires that you will not find on your wiring diagrams. Do not try to remove the harness from the relay unless you have forearm muscles like Popeye. Remove the attached relay(s) and then undo the two screws holding the fuel pump relay to the panel. I found it easiest to remove the knee bar and heater blower motor first, but if you have very short screwdrivers and small hands, you can probably manage less disassembly than I did.


Wiring Diagram of Relay
Posted Image B=Black W=White L=Blue G=Green Y=Yellow
Eliminate Less Expensive Repairs First
These six mystery wires monitor several important systems in your truck so that if any one of them fails, the electric fuel pump will not run. Before you unbolt the relay and spend $50 or more to replace it, first make sure that these systems are functioning correctly!

They are:

1) The ignition switch Accessory position (power to blue wire when ON)

2) The ignition switch Start position (power to White wire at START using Fuse #5)

3) The Alternator (power to White/Blue wire when running)

4) The Oil Pressure Switch or Oil Sending Unit (4WD) (Yellow/Green)

This is a wiring diagram for the fuel pump relay terminal that I created using the Haynes© color codes found in my harness – hopefully yours is the same. Use this to check continuity in your wiring. It’s better to find a broken or corroded wire now than to replace the relay and still have the same problem.


Repair Manual Discrepancies?
I’ve noted some discrepancies in my Haynes© Manuals which may or may not apply to yours as well.

1) The wire from this relay to the Body Harness Connector (ultimately to the Fuel Pump) is White/Black. Why Nissan used a White/Black wire from the relay to the Body Harness Connector (found under the carpet beneath the passenger’s seat) is a mystery to me. All other fuel related wires throughout the truck are Brown as is the connecting terminal in the Body Harness Connector which goes directly to the Fuel Pump.

2) The White wire connects to the fuse block at Fuse #5. In my two Haynes© books (Chapter 13, figure 3.1b), Fuse #5 is shown to be empty. I’m currently running a 10A fuse in this position and haven’t had any trouble. Also, pulling this fuse doesn’t seem to shut off any Start features other than the fuel pump (via the relay).

3) Not related to the fuel pump relay so much (but since I’ve breached the subject) the wire out of Fuse #1 (Ignition coil No. 2) should have been listed as WB and not WY. All other diagrams seem to show it correctly.


Test Your Fuel Pump Again
If you have not already tested your fuel pump by running a jumper wire to it, you can do it now. Build a short jumper wire and connect the Blue terminal to the White/Black terminal. When you turn the ignition over to the Accessory position, you should now hear the Fuel Pump running constantly (not recommended as a permanent fix)!


The Fuel Pump "Shutoff" Relay
Posted Image If you decide to buy a replacement, go with quality parts. Posted Image The red arrows indicate the contacts that probably need repaired.
Repair It or Replace It?
Assuming you’ve narrowed down your problem to this relay, you can order a new one from an online parts warehouse or your local dealer. However, you may be able to save a few dollars. What have you got to lose trying? The relay is already not working and you’re a do-it-yourselfer after all!

Here’s your little trouble maker once you’ve removed it from the truck. A factory relay is labeled Jideco and if you choose to replace it, they seem to last about 20 years.




On the back of the assembly are four Phillips screws. Once removed, the cover and insulator come off and you’re looking at the circuit board of the relay itself. On the opposite side are the resistors, amps, and the big coil that should trip the relay when all is well – but has probably failed. If you look at the solder points under magnification, you may notice cracks. If you’re careful, you can resolder these contacts and have your relay working again in a few minutes.




Now put it all back together, pat yourself on the back, and go for a drive. You just potentially saved yourself hundreds of dollars at the dealer!

____________________________________________________________________________________



One other thing. Be sure the Black wire at the electric pump is well grounded or the pump will not work.

#7 84 Nissan/Datsun Truck

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Posted 08 October 2011 - 02:59 PM

Thanks for all of the responses on my previous post. SO, far, the only way I have been able to make the fuel pump activate was to run a jumper wire and connected the Blue terminal to the White/Black terminal of the fuel pump. When I turn the ignition over to the Accessory position I now hear the Fuel Pump running constantly. The truck still does not run. Does this mean my Fuel Pump Shutoff relay is bad, or something else? I do not see any fuel going to the clear fuel filter. Please help, any other suggestions will be greatly appreciated.

#8 datzenmike

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Posted 08 October 2011 - 04:50 PM

Usually we don't start a second topic on the same general problem so I've merged it . The thing to do is just continue with the first post and keep going. This will keep everything together and neat.



You need these two to get the pump started during start up.

1) The ignition switch Accessory position (power to blue wire when ON)

2) The ignition switch Start position (power to White wire at START using Fuse #5)
(my wiring diagram shows power to the #5 fuse with the ignition in the ON and the START position)

So pull the plug off the relay and test for power on these two wires.....

You should have 12 volts to the Blue wire with ignition in the ON position, and the White wire when the ignition is in the ON and the START positions. I would check the #5 fuse. Swap with another 15 amp fuse.






You will need these two after the motor starts to keep the pump going. You don't have to worry about these just now.

3) The Alternator (power to White/Blue wire when running)

4) The Oil Pressure Switch or Oil Sending Unit (4WD) (Yellow/Green)

#9 84 Nissan/Datsun Truck

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Posted 08 October 2011 - 05:09 PM

Sorry about that and I appreciate all of your info. I will troubleshoot these items tomorrow.

#10 Sealik

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Posted 08 October 2011 - 05:53 PM

Thanks for all of the responses on my previous post. SO, far, the only way I have been able to make the fuel pump activate was to run a jumper wire and connected the Blue terminal to the White/Black terminal of the fuel pump. When I turn the ignition over to the Accessory position I now hear the Fuel Pump running constantly. The truck still does not run. Does this mean my Fuel Pump Shutoff relay is bad, or something else? I do not see any fuel going to the clear fuel filter. Please help, any other suggestions will be greatly appreciated.


Pump is running.... but no fuel?
Pull the fuel line off the pump that feeds the engine....flash up pump...no fuel?
If not...confirm you have fuel :D and then remove (twist off) base of pump...see if the filter is plugged.
You did replace the relay as seen here....not the smaller one next to it?

The Fuel Pump "Shutoff" Relay
Posted Image

#11 84 Nissan/Datsun Truck

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Posted 05 November 2011 - 03:27 PM

I finally got the fuel pump to work, but it still will not start. I ran another wire from the fuel pump relay to the fuel pump. Does anyone know of any troubleshooting areas I could try? All help is greatly appreciated.

John

#12 datzenmike

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Posted 05 November 2011 - 03:47 PM

Take air filter off and hold the choke open, pump the throttle and you should see a strong squirt of gas from the accelerator pump.
Check the sight level bull's eye on the front. Fuel should be near the dot.

If both are ok you likely have fuel. Next you need spark.

Pull one intake and one exhaust side plug wire and put an old plug in the end and lay on a grounded surface. Crank over and look for spark. Both sides should spark.

#13 84 Nissan/Datsun Truck

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Posted 05 November 2011 - 03:53 PM

Thanks, When I add starter fluid it will run until the fluid is burned off. I will thy these troubleshooting pointers tomorrow. I will keep you posted.

Thanks again,

John

#14 84 Nissan/Datsun Truck

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Posted 06 November 2011 - 03:13 PM

Today I had my wife pump the accelerator and I did not see any fuel in the sight window nor in the carb. Does anyone have any trouble shooting pointers I could try tomorrow? I appreciate all of your help.


Thanks,

John.

#15 datzenmike

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Posted 06 November 2011 - 03:45 PM

The pump is just forward of the right rear wheel on the frame. Pull the hose off and see if it is actually moving gas. You can hear it humming??

#16 84 Nissan/Datsun Truck

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Posted 06 November 2011 - 03:50 PM

I can hear the pump pumping when I have the ignition on. In order for me to get my fuel pump to work I had to use a jumper wire from my fuel pump relay. Is that ok? Thanks for all of your help.

John

#17 Ruck

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Posted 29 November 2011 - 06:46 PM

I've replaced my fuel pump twice in two years, so I wouldn't rule out a bad fuel pump even if relatively new. Is it possible for it to pump but not pump with sufficient pressure?

#18 84 Nissan/Datsun Truck

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Posted 30 November 2011 - 10:11 AM

Thanks for all of the help. I finally have my truck running. It needs a tune up now though. I ran a jumper wire from my fuel pump relay and I replaced a dry rotted hose running from the carb to the fuel line and know old black and blue is running. Thanks again.

John.

#19 schassisowner

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Posted 08 September 2012 - 05:19 AM

ok so i am having similar problems with my recently acquired nissan 720. I have narrowed it down to this relay being bad and am looking to replace it in the next couple of days. The original problem was the alternator was not charging my battery. Since this relay infact ties into the charging system could this be why? Its a brand new alternator, and was bench tested and came back as a good alternator.

#20 c10jim

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Posted 08 September 2012 - 08:25 AM

There is some great advice hear to help you fix your problem. I however would not head the advise about filling one pockets with relays. That could get someone banned for life at their favorite junkyard.