Arcolithe

so I've been diagnosing why my engine bay area isn't getting any fuel above .5 PSI.

New fuel pump, re-did the soft lines.

I think I've diagnosed that the hard line that runs along the front of the car is clogged somewhere. How hard would it be to replace this, or is it easier to gunk it out?


Also how do I check if my wiring harness is bad, I put the multimeter againsts where the pump connects to (behind the driver backseat) and didn't get any readings at all (with key in ignition)

Would it just be easier to buy an oem harness?

74RX4

iTrader: (10)

First we need to know what year and model your car is. Unlikely the hard line is clogged. Most fuel pressure gauges are notoriously inaccurate at the low pressures the 12A cars run at. What is the car doing that makes you believe it is a fuel delivery issue? Later model cars have a fuel pump relay that supplies power to the fuel pump only when the engine is cranking or running. You didn't mention replacing the fuel filter, but if you did the pump and the soft lines I assume you did. If you have a fuel problem, you need to start at the beginning of the fuel system. That would be the tank. Very common for these old cars to have nasty stuff in the fuel tanks. The pick up tube and screen become clogged which severely limits fuel flow. The inside of the tank ends up looking like this.

Cookboy

iTrader: (10)

^ yep. Search. 'Marine clean' for a good thread on the topic.

Jeff20B

iTrader: (13)

You didn't state what year your car is, so I had to do some digging. Looks like you've got an 84. How are you checking that your fuel pump works? Just hooking up your multimeter like you said? That won't tell you anything in an 84-85 chassis, other than it's not working. Why? Search newb!

Better yet, I'll give you the solution. There is an anoying relay up under the dash called the fuel pump cut relay. It does not allow the fuel pump to run when the trailing ignitor is not working. In other words if it fails, you get no fuel. Or if you turn the key to ON but don't crank, you get no fuel. Makes it tough for those not in the know to test their fuel pump on 84-85 cars.

The solution is to search noob! "fuel pump cut relay" There is an image and instructions I found on this forum (because I searched!) the other day when I was testing the fuel pump on an 85.

Arcolithe

i directly connected a 16 wire to the battery to a relay, to the pump. Pump works for sure. fuel comes out in very odd pulses (like 4 second burps)

Jeff20B

iTrader: (13)

It'll do that. It has to pump for like a minute for the bubbles to dissipate. I had to pump out 6 gallons of old gas from an 85 GS the other day.

Arcolithe

how long does it take? we let it run for an hour...

Arcolithe

so basically you guys said to search marine clean. I did and the main guides on how to use it are actually sea foam related.

Can't figure out what I need to look out for or buy with marine clean, if I should let it sit, run through the engine or what.

74RX4

iTrader: (10)

MARINE CLEAN

http://qr.absolutecoatings.com/QR-as...TankSealer.pdf


If I have no leaks in the tank, I just use the Marine Clean portion of the instructions in the pdf.

Arcolithe

alright still can't tell if it's the hard line or not, but I unplugged under the car and put the fuel line directly after the fuel pump into a bucket, turned the fuel pump on (hooked it up to a switch) and it didn't work. I put a multi-meter up to the switch and it was showing .24 on the 10A mode (no idea how to really use a multi-meter, bought it specifically for this car problem.)


I have a Mr. Gasket aftermarket fuel pump. I'm not even getting pulses of liquid anymore, just air (visible fuel fumes being pushed out).

Hand pumping the fuel line from the tank produces fuel, so I'm guessing it's my fuel pump even though it's brand new.
Mr. Gasket brand | Part #: 12S

Arcolithe

alright, still trying to diagnose the fuel. Kinda stuck since I can't figure out what my multimeter should read. It doesn't read the old oem fuel pump at all (even if it turns on)