my '86 loyale Carb fuel pump has only 12 volts going to it (not enough to run it) while the battery has about 13volts or more...the pump works OK when hot wired,but my haynes manual does not provide enough info ...does the pump run directly off the coil or starter switch or ???

im not completely sure about how the pump is turned on, but im pretty sure it turns on when the distributor turns. also, im pretty sure the pump gets the 12volts+ with the ignition, and the ground side is the switch that turns it on. theres a fuel pump relay somewhere along the way too

12 volts should be fine to run a fuel pump.

 

do what i did for a few thousand miles, ground the pump right there under the car, and run a how wire from the fuse box so its on whenever the ignition is on.

if the pump don't work when plugged into the original harness u may a problem with that plug. had that problem on my 82.

if the pump don't work when plugged into the original harness u may a problem with that plug. had that problem on my 82.

..I know it is not the "plug" because I went inside the car under the carpet to test the wire leading to the pump...had the same low voltage

..I know it is not the "plug" because I went inside the car under the carpet to test the wire leading to the pump...had the same low voltage

 

12 volt isnt low that is enough to run the pump.

12 volt isnt low that is enough to run the pump.

That is exactly what I thought...but the pump will only run and the car starts up when directly hooked to the battery which has more voltage

my '86 loyale Carb fuel pump has only 12 volts going to it (not enough to run it) while the battery has about 13volts or more...the pump works OK when hot wired,but my haynes manual does not provide enough info ...does the pump run directly off the coil or starter switch or ???

 

Hey Peter,

 

I've got a carb "86 that is hot wired to run off the coil. Previous owner did that. I suspect it's supposed to run through a relay, but haven't gotten into it.

 

If that's the case with your car, you have voltage but, it might not be able to carry the amperage to run the pump.

 

I'd be interested in how you resolve this.

 

Doug

Hey Peter,

 

I've got a carb "86 that is hot wired to run off the coil. Previous owner did that. I suspect it's supposed to run through a relay, but haven't gotten into it.

 

If that's the case with your car, you have voltage but, it might not be able to carry the amperage to run the pump.

 

I'd be interested in how you resolve this.

 

Doug

I will let you know, maybe in the next couple of days, hopefully it will not be to cold outside

when u hook the pump directly up to the battery where do u hook it on the pump

About the direct wire making it run ok, unless the original wire is almost broken you will still get 12 volts but it will not supply enough current acting like a resistor. The voltmeter is showing potential (12 volts) not what current is traveling thru the wire unless you measure for it with an amp meter. I would try to find out if that wire is pinched and almost broken some where. If it is down to only one or a few strands of the wire it will not supply enough current to run the pump but will still show the correct voltage.

If the wire is hot to the pump then grounded thru a relay or other source this is probably where you’re loosing the circuit. If the relay is dirty or the points are bad that will act as a resistor and drop the current. If it goes to a bad ground connection you’ll get the same results. If it goes thru another component then check those connections.

Hey Peter,

 

I've got a carb "86 that is hot wired to run off the coil. Previous owner did that. I suspect it's supposed to run through a relay, but haven't gotten into it.

 

If that's the case with your car, you have voltage but, it might not be able to carry the amperage to run the pump.

 

I'd be interested in how you resolve this.

 

Doug

Well Doug..I believe the best, easiest and safest way to deal with this problem is to find another relay box (or whatever they call this item which has many wires going into it)...for the time being I hooked the wire directly from the fuse box to the pump, until I can find what I need...this will not be easy since I drive the only carbed model for many, many, miles around

Another way to go would be to buy the "Holley fuel pressure Switch" Part # 12-810 thru for ex. Amazon.com ..$20...I have to further check and see if it fits on

Well Doug..I believe the best, easiest and safest way to deal with this problem is to find another relay box (or whatever they call this item which has many wires going into it)

 

I looked at an '87 FSM for a carb car and didn't see a "relay". What it does show is called a "REV sensor", Black in appearance, 6 pole..., that the fuel pump runs through. I'm hoping to take a closer look at the car tomorrow if I have time.

There is a relay of sorts - it is NOT a typical relay.

 

The block box you are refering to is a fuel pump control unit. It is designed to allow the fuel pump to run ONLY durring these conditions:

 

1. For a short time (3 seconds I think) when the ignition is first turned to "run".

 

2. When the ignition is in the "start" (cranking) position.

 

3. When the engine is running.

 

To do this it uses the tach signal, and the ignition circuits. Internally it's got a timer circuit, and a relay, and some other circuits to supply power based on the tach signal.

 

What I know of these is they are fairly simple, and pretty rugged. They are neccesary saftey items to prevent the engine from running after an accident. I have also yet to see one actually fail - although water intrusion would probably kill one as well as it kills any other relay. EA81's and EA82's with carbs (non feedback) all have them and they don't cause any issue.

 

Try bypassing it and see if that makes the pump work with the stock wiring. At least that will tell you if it's internal relay is damaged. IIRC they also come apart pretty easily and you could check the guts and see if you can clean the contacts, etc.

 

GD

the power comes off a relay mounted just above the ecu on the steering column.

 

there is a green and a brown relay, i believe the brown one is fuel

 

even if you have 12 v at the pump make sure it is ggrounding at the body as well.

 

make sure the relay is getting power.

 

yes it its possible to hotwire the pump to the coil/ign circuit. you may as well get the relay to take off from there. check allt he wires to the relay since it is turnrd on by a ground int he ecu

the power comes off a relay mounted just above the ecu on the steering column.

 

there is a green and a brown relay, i believe the brown one is fuel

 

even if you have 12 v at the pump make sure it is ggrounding at the body as well.

 

make sure the relay is getting power.

 

yes it its possible to hotwire the pump to the coil/ign circuit. you may as well get the relay to take off from there. check allt he wires to the relay since it is turnrd on by a ground int he ecu

Thankyou for trying to help, but model is "carbed"

i would suspect a grounding issue, if the voltage is lower than normal, corosion is usually th e suspect, i had fuel pump issues (85 gl carb) and when i cleaned the ground for the coil the car ran perfect, also dont forget to use a electrical contact grease. i live in salt country and have never had a grounding issue after i cleaned and greased a grounding point.

There is a relay of sorts - it is NOT a typical relay.

 

The block box you are refering to is a fuel pump control unit. It is designed to allow the fuel pump to run ONLY durring these conditions:

 

1. For a short time (3 seconds I think) when the ignition is first turned to "run".

 

2. When the ignition is in the "start" (cranking) position.

 

3. When the engine is running.

 

To do this it uses the tach signal, and the ignition circuits. Internally it's got a timer circuit, and a relay, and some other circuits to supply power based on the tach signal.

 

What I know of these is they are fairly simple, and pretty rugged. They are neccesary saftey items to prevent the engine from running after an accident. I have also yet to see one actually fail - although water intrusion would probably kill one as well as it kills any other relay. EA81's and EA82's with carbs (non feedback) all have them and they don't cause any issue.

 

Try bypassing it and see if that makes the pump work with the stock wiring. At least that will tell you if it's internal relay is damaged. IIRC they also come apart pretty easily and you could check the guts and see if you can clean the contacts, etc.

 

GD

this morning I pulled the "fuel pump control unit" box and was surprised to see it resembled a smaller version of a computer motherboard..anyway it was dry and clean looking inside...at this point (maybe wrong) I am taking the your position that the control box is still good...the positive side of the wire coming from the fuel pump is "green" with "2 small red strips" (86 loyale) and the only place that I found under the dash of a wire with the same color was going to the ignition switch... at the moment I am unable to check the voltage at the ground wire on the Ign switch to see if the votage is the same as the battery...on 2 different occassions I drove over some large pot holes and immediately the car was turned off...it would not re-start until the next morning when the morning is cold...so my theory at this point until tested would be that a new/used igniton switch would be needed

Finally, I believe to have found the problem..the new fuel pump with only about 3 hundred miles on it draws to much current and will only work when attaching a 2 amp battery charger directly to the pump...sounds like it is moaning and laboring hard...the car motor ran perfectly with charger attached to the fuel pump for a couple of minutes..then I tried to operate the pump directly from the battery within the same car, it wouldn't run...

The new pump only was getting maybe 3-4 amp max from the 2 amp charger....... You still have a bad connection, a ground problem, pinched wire or bad points on the relay... If you have a DVM, or OHM meter you could check continuity of the wires and condition of ground connection. Also depending on the circuit configuration you should be able to use a wire and complete each leg with that wire and jump along until you find the bad wire or connection. Bret

The new pump only was getting maybe 3-4 amp max from the 2 amp charger....... You still have a bad connection, a ground problem, pinched wire or bad points on the relay... If you have a DVM, or OHM meter you could check continuity of the wires and condition of ground connection. Also depending on the circuit configuration you should be able to use a wire and complete each leg with that wire and jump along until you find the bad wire or connection. Bret

..definitely to do when, hopefully it stops raining...One thing that I don't understand:..why does the pump Not run when attaching separate jumper wires directly from the battery...even the old one ran when I tested it this way

What type of ground did you have??? Bret

What type of ground did you have??? Bret

I ran 2 long wires from the battery to the pump..the ground was the battery terminal

the problem was found to be the "fuel pump control box"...some of the perceived complications of my own testing for "ground" etc. was made more difficult because one of my testing wires was poor (broken) which would give at times a "no voltage" reading...