Hey, I’m having a problem with my 1993 EG (d16z6). It’s not starting and it’s because the fuel pump isn’t priming.
I’ve tried:
1. A new fuel pump
2. another main relay (that I’m pretty sure works and can hear both clicking)
3. Measuring the voltage at the plug that goes into the pump: 10.6ish
4. Checking continuity between + pin outside fuel pump assembly and + on plug that connects to the actual silver pump inside tank. (Same for -, and there is continuity on both).

There is “continuity” between the + and - pins on the actual pump itself. The one I thought was bad has 5.4 ohms resistance and the new one is 1.4 ohms. I thought it would be in the hundreds because they’re separated right? I jumped the old one with a 12v battery and it worked and spat some gas onto my desk. I’m sure the other one would work if I jumped it, I’m just confused on why it’s not priming when the voltage goes close-ish to 12 for 2 seconds like it should be priming. The voltage at the plug is over 10 volts. So it’s getting 10 volts at the plug and there is continuity all the way to the ground/frame of the fuel pump assembly. So the pump itself should be getting over 10v and it’s rated 6-18v. How come the pumps work when jumped but not when they’re getting 10.6v?
And is there supposed to be such low resistance between the -/+ pin on the actual pump itself?

Note there is a voltage drop because when the relay clicks to turn the pump on/off, the voltage at the pump plug is 10.6 but the battery voltage stays at 12.5. But 10.6 should still be enough to turn on the pump right? Unless there’s internal resistance or shorting or something right? But the old one worked when jumped, and the new one is new lol.

 

What brand of fuel pump did you install in the car ??? You are checking voltage... but have you checked amperage draw when you turn the key ??? This is a common problem with cheap/fake EBay and Amazon supplied fuel pumps.

 

I don’t know or care about the brand of fuel pump. I bench tested the old one that’s having the same symptom (not turning on) and it worked with a 12v lithium battery.
I can’t get to the plug when it’s plugged into the pump, so I’ve only been measuring voltage with the plug unplugged. I’d prefer not to have to splice into the wires.

What I’m asking for is a good range of “normal” resistance between the +/- pin on the pump itself. Couldn’t find the spec. Also, does anyone know if it should work or not with the voltage it’s getting? And if so, why did it work on the bench test, but not with 1.6v less?

 

So the weirdest thing just happened. I set up a charger to fully charge the battery. It ended up overcharging it to 13.5v with car off, but I don’t think it matters. Once I got that reading, I wanted to try it out, even though it’s almost 4:00 am. I measured the voltage at the plug, and it went to 13.3v for 2 seconds, then back to 0. Just for clarity, I switched the main relays to see if there was a difference and I got 13.3v at the plug again. Good.
So I plugged it into the pump (out of the tank) but all wires connected and turned the key and it didn’t prime. Ugh. So I switched the pump within a minute (didn’t even take the hose clamps and everything off, just put the plug into the other pump) and plugged it in and turned the key and it still didn’t prime. Double ugh. Just to make sure I’m getting no voltage drop between the 2 plugs on the fuel pump assembly, I measured the voltage at the plug that’s normally inside the tank. Turned the key and the voltage was 10.3v….. I thought I found the problem, then I measured the voltage at the out-of-tank plug and turned the key and got 10.3v….. Even though I measured 13.3v at that plug like 2 minutes before. I did it 3 times just to make sure and it was still 10.3v. I thought the car battery might be bad and I measured that and it’s still at 13.5v

Can someone please explain how that could be? It’s late so I’m not trying it again tonight, but something tells me in the morning that plug will have 13+v when I turn the key and then 10.something after I turn the key with the pump plugged in. And why did it stay at 10.3v at the plug even after I unplugged the pump?

 

Okay so it is now the next day.
I measured the battery voltage at 13.12v. I measured the voltage at the plug when primed and it’s 9.52v for 2 seconds. I tried this multiple times and switched the main relays again and still 9.52v. So I plugged the pump in to see if the voltage changes and it didn’t prime, of course, and when I unplugged it and measured it was still 9.52v when priming. Just to try a quick fix, I put a known good ECU in and same thing, 9.52v when turning the key and no priming when pump is plugged in.

please somebody help me on this. I know this tech forum has a lot of smart people, I just can’t figure this out and I use this car for work.

 

Has the car been modified at all. Is the fuel pump wiring and connector oem.

 

No major modifications besides coilovers. The connector is oem.
I just jumped the “new” fuel pump with a 7.7v battery I made and it turned on. So I’m getting closer to understanding, I guess.
How come there is voltage at the plug and seems like there’s no short, but when the pump(s) plugged in the voltage assumably drops? It’s like the short would be at the plug, but it’s not because it works normally.

 

Whats it measuring while trying to crank it. Make sure there is no corrosion on the terminals and get all your grounds sanded and cleaned. Especially the fuel sending unit ground. Which mite on the driver side door seal depending on chassis.

 

I’ll find out voltage when trying to crank. I don’t even crank it anymore because I know it won’t start without fuel.
is the fuel sending unit the part right next to the pump assembly?

I cleaned the terminals and have sanded and cleaned every ground I know of (engine bay ones, and the one behind dash driver side)

 

Okay it has gotta be a short somewhere in this circuit. Pls anyone who’s knowledgeable in EGs help me.
I tried the fuel pump with a 7.7v battery and even 4.05v and they both still turned it on, but not as powerful obviously. So that led me to believe it’s getting 0v, and I spliced into the wire and measured with it plugged in, and yes, 0v. When it’s not plugged in, 10.something volts. So plugging it in creates the short. It’s not a short in the whole car because I tested and was able to turn on the headlights or ac while that 2 seconds of priming is going on. So it’s a short probably close (electrically) to the fuel pump.
Again, when it’s not plugged in, there’s good voltage at the plug, but when it’s plugged in there’s 0v.

I’ve replaced fuse 24 just to be safe. I have another thread in the DC2/EG forum explaining how I have the battery light come on sometimes, so I tried unplugging the alternator to see if that’s the short and it’s not. Still no priming. I jumped relay connector 1-7 and 5-7 and neither of them got the pump to prime.

Please someone help me

 

Something is draining the power, I just want to know what it is or how to find it.
I put the multimeter leads into the pins that go into the main relay. I measured voltage between 1-7 and when it’s supposed to be priming it’s 0v, and then goes up to normal voltage as soon as it clicks when the priming is supposed to be done. It’s the exact same for voltage between 5-7.

This means that as soon as it sends power there, it’s drained by something else acting as a short? Would that mean the problem is a short somewhere between the main relay and the fuel pump?

 

Well I got it running and I’m 90% sure the problem I found/fixed is the permanent solution.
I searched my problem more specifically and found 1 thread on here and another on another website that discussed the c415 / c551 plug, behind the main relay/hood latch lever. When I found it, I noticed the yellow/green wire for the fuel pump was discolored and dark near the plug, likely from heat. The pin inside one of the plugs was pushed back and a little corroded. I took it out, cleaned it, pushed it all the way in, and plugged it back in and the car starts! I bet it was barely making contact for years and may be the cause of my other electrical problems.
I’m glad lol