FP & MAF Relays share continuity?

[SC74]

Not sure the best way to title this thread.

Using this diagram on Ryan's site (third diagram down) that Chuck pointed me to, I was checking continuity on my relays and fuses to determine which was which (all started with my fuel pump issue).

My first step was to confirm which relay I thought was the FP and checked it with the inertia switch. Checked positive but I still checked all of the other relays and the MAF relay also has continuity with the inertia switch cratchhe:

I got this same cross - continuity again while checking other things but can't remember exactly what it was. I think it was when I checked the MAF plug to the MAF relay and also got continuity on the FP relay.

Is this supposed to be? If so, why? The diagram sure does not show anything like this supposed to be happening.

[SC74]

Here is the diagram I am using.

[nhopman]

You shouldn't have continuity from the FP relay to the MAF. The relays should only turn on the systems that they are supposed to run.

However, They do all share a single input from the key on input, a ground wire (FP grounds through the test plug, the rest go directly to gorund). Plus since all the fuses share a common connection to the battery, you could get continuity there as well. if you are testing the wrong terminal.

I wish I could be more helpful and just give you an answer, I can follow a diagram and wire things up most of the time, but I can't say I have a complete understanding of EFI wiring.

I marked mine with a silver sharpie when I put the harness together and noticed the other day that the markings are barely visible, so when you figure out which one is which, be sure to make them with something more permanent.

Good luck, Nick

[nhopman]

You are checking for continuity with the key Off correct?

If the key is On, then they will have continuity with each other.

Nick

[chuzie]

Unplug the computer when doing this also. You cannot rely on anything with the computer installed. Also reference this diagram. They share the same power source.

[SC74]

I like that diagram Chuzie.... saved!

I am doing this continuity testing with the key off. I also removed the fuses to isolate them from each other. I do share a common ground with three, and the fuel pump separately as Nick mentioned so I'm good there. I also do share an ignition run with all four relays. The way mine is mounted, the top blade (the one that is turned the opposite direction from the other three) is the "on / power" terminal. Without any fuses or relays, the inertia switch wires share continuity with both the FP relay and the MAF relay. When I checked the MAF vs. the MAF relay it has continuity, but also has continuity with the FP relay. The coil ONLY has continuity with the ignition relay.

I am basing this all on my "sound" on my multimeter. I was stretching to touch both places myself so went by sound rather than by ohm value. Viperwolf on Classic has asked me to get the actual readings and see if there is a strong and a weak. I will see, but I did have some "weak" continuity testings that only clicked on the meter rather than a loud constant beep. I will get Jess to help me tonight so I can get my eyes on the meter too.

Update later on....

[SC74]

Once I rigged it so that I could see the meter and measure ohms rather than just continuity, it shows that the cross-continuity is at about 4 ohms. The correct relay pegs out at 0 ohms so my continuity tone must be set higher than 4 ohms.

Still haven't solved me fuel pump relay issue :banghead:

[chuzie]

What is the problem? Did I miss something?

[SC74]

I sporadically get good fuel pressure. Sometimes it will run perfectly and other times it starves for fuel. By grabbing the fuel line it has steady pressure when running right and on/off pressure when not running well. I bypassed the inertia switch - same problem. I swapped fuel pump relays - same problem. Still hit or miss. It throws code 95 about FP ground and everyone points that to a relay so that's what got me testing continuities.

Last time I got it to run well I had just checked my fuel level by opening my fuel cell. I thought it was a vent problem, but I have not re-created the problem since. Maybe it's gone for good, who knows. My luck it will come back at the worst possible time. I just want to know what to do to fix it when it does come back.

[chuzie]

I had that issue once and it was a venting problem. the times it gave you code 95, did it prime the fuel pump at the beginning of the test? have you tried resetting the computer (unplug for 15 minutes)?