But I can't test with a pressure gauge if the fuel pump isn't running, correct? I just sprayed into the throttle body to make sure the car will actually start if it gets some sort of "fuel". So I figured I might as well check the wiring first since I can do that without buying or borrowing a gauge. I may be doing this all out of normal order, but I'm not a fully equipped shop with every tool or gauge on hand, so just trying to rule out or confirm what I can with what I have to work with. I think the fact the car started with a little squirt in the TB at least tells me it will start, so that narrows it down to the fuel pump or wiring. Maybe?

 

Given your available tools, that’s reasonable.

George

 

I'm back to working on the Jimmy since I hit a deer with my backup car lol. I rented a fuel pressure test kit. Battery is a little low, about 11.8v and charging right now, in case that might affect the results. Turn key on, it goes to 44 as pump primes, then drops to 42. After 10 minutes it's at 38.

I haven't been able to test at the pump connector yet. The way it faces, if I could get it unplugged I'd be able to get a better view to insert the back probes then plug it back in. But I can't figure out how to release it. Doesn't seem to have a place that depresses on top. Do you know exactly how to release it? If there's a tab underneath I think I could use a screwdriver to push it. Just don't want to mess around and break anything.

 

I believe the line release on the tank end has two wings on opposite sides that get depressed. You need the other end though heading to the motor which is a threaded flare fitting.





George

 

I'm talking about the power connector, to test that last wire run from relay to pump. You said to back probe and check while under power load. I forgot to say I did clean the ground on top of the crossmember behind the tank and that made no difference. Also I left pressure gauge connected for 30 more minutes and it held at 38.
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Oh the power connector. I don’t remember what type of connector is used there. If you can photograph it I might be able to help but if your trying to back probe can you get probes in behind the connector while still connected? That said your next move is to measure pressure at the fuel filter. If it passes, it’s not the pump or it’s wiring.


George

 

Isn't the pressure too low? I thought I read somewhere on the forum that it has to be at or above 50 to start on this vehicle.

I finally got the connector off last night but was getting too late to do anything else. Only way I can reach it is from the spare tire space, and back of the connector faces more to the front of the car, so couldn't see to back probe.

 

Yes your fuel pressure is too low but you don't know yet where the problem is. The second half of the pressure test at the fuel filter tells you where to go next, the gas tank or the intake plenum.

George

 

I have these results from electrical testing tonight. Battery itself reads 12.1v. With plug connected to pump and using back probes, I get 11v at the pump connector when I apply battery positive directly to pump prime terminal by relay. If I use the key to prime for the roughly 2 seconds it goes up to about 11.3 and drops off as pump stops priming. I checked resistance on the ground, or ohms, not exactly what that symbol means lol. Couldn't find a good clean ground underneath so ended up clipping a lead to the tail pipe and I get a solid reading of 4.3.

 

Oh and I can't be sure I had a really good connection on the back probes. Theyre like little needles and took me a while of one handed finagling to get them to insert fully at the wires where they enter the connector.

I didn't try to test pressure at fuel filter yet because I'm working with vehicle flat on the ground, and I remember how hard it was to get that connection loose before. Plus I keep seeing people have asked what size fitting is needed there....