Fuel Delivery Issues...???

[FlamingTaco]

I am helping a neighbor with his 95 3.3L Caravan. His Contour died this summer due to abuse (many years spent delivering newspapers), and now him and his wife have this many working cars -->0, so I’m feeling kinda sorry for him.

He knows squat about cars, but still managed to formulate the thought that the fuel pump was bad. I did an ear check to see if it was priming, and heard nothing. A few minutes later I had determined good spark, good air, no fuel, and so set about looking at fuel delivery.

I quickly checked the fuel relay and found it functioning ok. I then found there was an “auto-shutdown” relay, and checked that as well. I figured it might serve to replace an impact triggered emergency fuel cutoff switch most cars have, as we could not find one. The Chilton’s manual he has did not show one, but I do not entirely trust Chilton’s manuals.

At this point, I decided to drop the tank and check it out there for the sake of doing it. I pulled the fuel pump, emptied it and held it in my hand while he put the key to “run”. It did nothing. At “start”, nothing happened.

I hooked up the new pump and checked it out. At “run”, it definitely primed. Great! At “start”, nothing. What the ????

I hooked up the old pump, tried it again, and it primed, but did not spin during “Start”. I check the new one again and it did the same, so I figured I must have not had the plug on firmly when I initially checked the old pump. Both pumps did the same thing, twice each! They spun to prime, but not during start.

I buttoned the tank all up, and checked the supply to the pump at the connector under the left side of the van, just past the driver’s door. Same thing. Voltage during prime, but not during start. I tore open the engine bay fuse and relay box and checked the grn/blk wires coming off the fuel relay. One goes to the fuel pump, the other to the O2. 12V during prime, and 12V during start. What the ??? I do a continuity check between the wire at the fuel relay and at the connector under the chassis. This is the last connector before the fuel pump wires take a jog off of the chassis and onto the fuel tank. 0.2 ohms. Hmm. Ok, I pull the fuse that provides the 12V supply that is relayed to the fuel pump, and check continuity during prime and run to rule out an unseen relay, and it stays rock-solid at 0.2ohm the whole time.

Now I check under the chassis for voltage between the hot and chassis, and again between the hot and ground supply for the fuel pump. 12V at prime, 12V at start.

Crap!

I check the fuel lines; no fuel pressure was or is being generated. At one point during all of this, we did actually get some fuel to squirt out of the schrader valve, but now, nothing!

So, at times, the electric seemed flaky, but at others, the fuel pump seemed flaky! Maybe the fuel pump is running, just so silently that we can’t hear it, and the fuel pressure regulator is flaky? Someone at NAPA mentioned the O2 sensor (shares a common hot supply with the fuel pump, and he did get two O2 codes), but it still does not make any sense. We pulled the plug to the O2 and double-checked, and this seemed to have no impact.

Maybe it’s me that’s flaky? Any ideas?

[drummertom]

Maybe I overlooked it but I didn't see the filter mentioned anywhere. Did you change it?

[FlamingTaco]

Originally Posted by drummertom

Maybe I overlooked it but I didn't see the filter mentioned anywhere. Did you change it?

We are going to, but I cannot see that as being the problem. Clogged filters cause poor performance for awhile before they become so clogged that the vehcile does not run. This one went from running fine to not even starting in no time at all. Also, there is not fuel pressure building in the rails most of the time. By no, I mean zero pressure. Open the valve and nothing comes out. Most vehicles will tolerate a 30% drop in rail pressure before you cannot get them started, but then you still have fuel rail pressure. We have none.