sft3303

Hey guys,

I just got done swapping out a bad engine from my 1990 N/A coupe, and went to try to prime the fuel system and I'm not getting any pressure. I tried to prime it using the yellow two prong plug/jumper, and got no fuel in the filter. I tried simply cranking it to try to get it to prime, no fuel in the filter. The EGI fuse is good, and there's no sound of the pump when the jumper is used. The Haynes manual isn't giving me anything at this point, and I definitely want to avoid spending $130 on a new fuel pump. I've looked around on here and haven't found much by way of fc3s s5 issues, and I'm not really sure what to do next. Think someone can help me out?

Any help is appreciated.

Thanks,
Jimmy

satch

iTrader: (1)

Make sure the 15 amp Engine fuse is good as it powers the fuel system.

TODAFD2

and also the engine fuel pump relay!

sft3303

15 amp engine fuse is under the dash, correct? All of the ones (like 80, 60, 100 amp fuses) in the box under the hood were good. And how can I test the fuel pump relay for faultiness?

satch

iTrader: (1)

Yes about the location of the Engine fuse.

The relay is located under the dash and to the right of the steering wheel column. It is Yellow and Black and has a total of five wires, three on the top row and two on the bottom. Top row far left wire has voltage w/key to start ( Black/White or Black/Red wire). Top row center wire has voltage w/key to on (Black/White wire). Top row far right (Blue wire) has voltage w/key to start and has voltage if the engine is running or if the fuel check connector is jumpered "and" the key is to on.

sft3303

15 amp fuse was good. Replaced with a new one for good measure.

Voltages on the fuel pump relay plug were good, and the relay clicks when i plug in the jumper cable on the priming plug. I'm getting no voltage at the pump though, like if i put my multimeter pickups on the two terminals on the pump, there's no voltage. Could a bad relay cause this? There's voltage going to the fuel level sending unit, so i know the harness isn't unplugged :/

Any help is appreciated, and thanks to those who have helped out thus far. You guys are an invaluable resource.

satch

iTrader: (1)

Where the Rear harness plugs into the fuel pump the plug has four wires and the Black wire is the ground wire and the Blue/Green wire is the voltage wire. Are you using these two wires to take the voltage measurement?

And the Blue/Green wire(s) run to the Fuel Pump Relay so perhaps the problem lies there. If you took the voltage at the pump properly then you'll want to check the wires at the Fuel Pump Relay. This plug has 6 wires. If everything checked out at the Circuit Opening Relay as you stated then the Blue/Red wires at the 6 wire plug would have voltage ( either w/key to start or key to on and the jumper in place) and if so then the voltage would pass onto the Blue/Green wires.

sft3303

I was going between red and black, and was getting voltage at that point. Nowhere else. but when i went between the two points that the pump picks up off of, i got no voltage. which leads me to believe the problem is not with unplugged harnesses, but with something determining whether or not the pump is to get voltage (i.e., a relay problem. The fuel gauge works too, so that also backs up my thesis).

I've dug a bit more into the Hayne's manual, and it's saying that the EGI main relay can cause this as well, and gives me a check test to do to see if that could be the problem. Any other ideas?

satch

iTrader: (1)

I added some info in my previous post. So you checked for voltage using the pigtail harness of the actual pump? Try the wires suggested above that are part of the Rear harness in addition to checking out the info related to the Fuel Relay.

sft3303

Fuel pump relay plug has 6 wires? Thought it only had 5 in a six plug harness? I'm assuming we're talking about different relays, where do I need to check, and what is it I need to check? Which one is the Circuit Opening relay and which is the fuel pump relay?

I took the voltage measurement at the terminals at the pump, and also at the two prong connector on the underside of the fuel pump mounting plate ( the large base plate that screws into the top of the tank). both places measured 0.

satch

iTrader: (1)

So if the Circuit Relay worked as supposed to then check the Blue/Red wires at the Fuel Relay which is located under the air box near the AFM.

sft3303

Okay so the circuit relay is the one under the dash (yellow/black) and the fuel relay is under the air box (or where it used to be before the p.o. took it off :/ ). Am I checking for a voltage between the blue and red wires? Or is this the same blue/red wire at the circuit relay and we're checking this wire vs. the ground for a voltage?

Sorry for all the questions, but i'd hate to get out there and have no clue what i'm doing

satch

iTrader: (1)

Blue/Red means a Blue wire with a Red stripe, so this is but one wire and not two and yes, this is the same wire at the Circuit Opening Relay (under dash) that you already checked, so the fuel relay (near AFM) accepts the voltage from the relay under the dash and then passes it to the pump. If there is voltage on the B/G wire as it should, but not on the Blue/Green wire at this same plug, then jumper the voltage from the Blue/Red to the Blue/Green wire and then after finding voltage on the B/G wire then check for voltage at the pump once more. If you need to jumper the two wires the Fuel Relay then leave the 6 wire plug disconnected after the jumper is in place. Only one jumper wire is needed.

sft3303

Are there any negative drawbacks to leaving the b/g wires jumpered permanently? Is that what you are suggesting to do if the case is that the voltage is not being passed along from the fuel relay?

satch

iTrader: (1)

No! If the Blue/Red does have voltage but the Blue/Green doesn't then you jumper one of the Blue/Red to one of the Blue/Green wires so the voltage at the Blue/Red passes onto the B/G wire. You don't jumper two wires of the same color here.

sft3303

I got that much, sorry if it wasn't clear. I'm going to go check this out, thanks for the help satch. I'll let you know in a few hours how it goes

sft3303

I checked out what you suggested. I have voltage at the blue/red wire at the circuit relay (under dash).

Here's the thing: The 6 pin connector/relay under the airbox has 3 blue/red and 2 blue/green wires. and one green/red (irrelevant to our conversation, I'm assuming). I had no voltage pass from any of the blue/red to the blue/green.

If it helps, what I did was insert one multimeter probe into the socket of one of the blue/green wires, and the other probe into one of the blue/red wires. repeated this until all combinations of blue/green and blue/red wires had been tried. voltage never passed through any of those combinations.

I also tried simply jumping the wires with a short wire jumper, in all of the same combinations as mentioned above. Each time i tried this, I'd go to the back of the car and measure the voltage from the blue/green wire to the black wire on the 4 pin fuel pump pigtail.

Am I missing something here? I'm contemplating having a mechanic look at it, but I really don't have the money for that right now.

satch

iTrader: (1)

When you measure for voltage while using a multimeter you need a ground source. Neither the Blue/Red wire or the Blue/Green wire is a ground so you measured for voltage in the wrong manner. To measure the Blue/Red wire requires the Red meter lead to be stuck into the back of the plug where one of the Blue/Red wires resides and the Black meter lead goes to a suitable ground like the negative battery terminal or the alternator housing. To measure the voltage on the Blue/Green is done just like the B/R wire just that the Red meter terminal is moved while the Black meter terminal goes to the same spot. So you did have voltage at the Blue/Red wires at the 6 pin plug? Correct?

sft3303

I was not able to get a decent reading at the 6 pin, due to my ineptitude with a voltmeter, haha. I wish i could just have this kind of conversation with a knowledgable rotary person IN person. I'll get more info to you when I can, you've been most helpful.

satch

iTrader: (1)

When you take the readings of the Blue/Red wire at the 6 pin plug and find voltage then proceed to measure the voltage of the Blue/Green wire. The plug needs to be connected to the Fuel Relay to measure the voltage on the Blue/Green wire but not the Blue/Red wire because the Blue/Red is before the relay but the Blue/Green is after. If you find voltage on Blue/Red but not Blue/Green then you need to remove the plug and jumper the two different wires and leave unplugged then recheck for voltage.

sft3303

Found the issue, and I feel like an idiot. It was the "anti-theft" switch that was hidden under the dash that shut off the fuel pump. So it's good now, the pump is working amazingly now. In fact it blew one of my hoses halfway off the barb, spewing gas over the engine. Replacing that clamp/hose asap...