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Twice in the last two weeks, my FD has shut off on me while driving. Both times, I pulled the sending unit out on the side of the road, and both times the feed line was dry. Set my camera up with the fuel pump connected outside of the car, and cranked it. Fuel pump wasn't spinning. When I got my car home, I bench tested the pump by itself and the pump while connected to the rest of the sending unit, and it is functional. The pump is a Walbro 350 that was installed last year. After this, I jumped the fuel pump using the diagnostic port, and checked for continuity at the rear harness plug that the sending unit connects to. I was getting 11.7v with the key in the ON position.
I was pretty confused at this point, so I took the jumper wire out of the diagnostic port, and with my multimeter hooked up, I set my camera up and watched the voltage reading while I cranked the car. Was getting about 10v (battery is a little old, and I had been cranking it quite a bit). So the pump is functional, AND I'm getting continuity at the connector while cranking. So why did the car shut off and kill power to the pump? As a last ditch effort, thinking that maybe the bulkhead connector at the top of the sending unit was bad, I reconnected the pump, positioned my camera and cranked the car over. Pump spun no problem. This tells me there is some sort of intermittent connectivity issue.
I know on my old Hondas, there was an issue where the solder joints on the main relays would develop hairline cracks, and when the car would heat up, they would expand and cut power to the fuel pump until the car cooled back down. However, when my FD shut off on me, it sat for 3-4 hours and never even attempted to start. I'm pretty stumped and I'm considering rewiring the fuel pump to its own circuit, but I'd like to diagnose the problem before I start hacking stuff up. Thanks in advance.
Edit: The car does have one CEL code, which is #06 for vehicle speed sensor - no signal. This confuses me a bit, since my speedometer is still functioning normally. Could this be related?
The most common reason for the fuel pump to crap out like that would be the connector at the top of the fuel pump hanger. You may have intermittent contact there and it gets worse when hot. That fuel pump is drawing a LOT more current than the stock pump.
Pete has a really good pictorial of a good, quality way to upgrade the electrical connection going into the fuel pump hanger -
Thanks for the response. The fuel pump in the car was put in by the previous owner when the stock pump died. I suppose I'll be looking into upgrading the electrical connection, then, because I am not really sure where else to turn.
As far as the Code 06, I read through the troubleshooting guide in the FSM. Since the speedometer is functioning correctly, I'm going to have to manually inspect the harness condition and check for a short circuit as well as check the physical condition of the sensor. I don't notice any symptoms related to that code, and my only options according to the FSM are to repair the harness or replace the sensor. This sensor is located on the drivers side on the transmission, correct?
I was considering the fuel pump rewire as a solution to my problem, but after additional research, it doesn’t sound like that would be ideal, as it would be supplying much more fuel and, since I’m on stock ecu, there’s no way for me to adjust the fuel maps to compensate.
I have a few questions:
1. Is my logic correct, or should the stock ecu/regulator compensate for the extra from the rewire?
2. If I keep the walbro 350 that’s in it now, and I upgrade the wiring, can I get away with depinning the stock bulkhead and repinning it with 12awg wire?
3. Would it be easiest, safest and more cost effective to drop down to a walbro 255 or a TT supra pump? The car is pretty much stock, and I’m just trying to drive it reliably, so if I can downgrade the pump and not have to worry about the car shutting off on me or upgrading the pump, I’d almost rather do that and hang onto the 350 if I decide to add power.
At this point in my ownership, I just want to drive the car but it’s at the point where I don’t even feel confident pulling it out of my garage out of fear that I’ll lose power to the pump and get left stranded. Any help is GREATLY appreciated
Thanks for your input, Dale. I've scoured the forums to get as much information as I can hoping that someone else has had this issue. My plan is to jump the pump using the diagnostics port while it's out of the car, and jiggle the wires and harness around to see if I can replicate the issue and pinpoint where the problem is (if it's not heat related).
The pump that's in it now looks to be a direct bolt-in replacement. The stock hanger is in pretty good shape, other than some corrosion, and doesn't look to be modified. The only modification I see are the wires from the Walbro spliced into the factory wires coming off of the blue bulkhead connector. I will snap a couple pictures and post them when I yank the assembly back out.
If I decide to just swap the pump out, do you have a recommendation on which to use?
I had this problem at the beginning of the year. I did a Chuck Westbrook FP rewire with 2 Walboro 450s in a surge tank setup.
The ultimate cause was that the pumps were drawing too much amperage for the "low load" voltage path to the FPs. I have since switched to a much smaller FP and new tune. No FP voltage issues since.
Thanks for your input. Sounds like I'll be searching for a smaller pump to switch to, then. I want to do some additional troubleshooting on the connection as well because I still have a feeling that there's a connectivity issue related to it. The other day after work, I jumped the FP using the diagnostics port, checked for continuity at the plug and was getting 11.7v. Then I plugged the fuel pump in, and it didn't spin. This is the direct opposite of the results I got after troubleshooting a couple days prior. I'll switch to a new pump to avoid the issue in the future, but I'm betting there's still a connectivity issue between the bulkhead connector on top of the hanger and the pump itself. Just between those two, there are 4 connections to troubleshoot.
Update: I did a little bit of troubleshooting. Jumped the pump using the diagnostic port and plugged the pump in outside of the car. I wiggled around the wires going from the pump to the bulkhead and was able to get the pump to kick on and off. I believe the connectivity issue is at the splice where the walbro wires connect to the oem wires.
I took some more pictures and I also depinned the blue connector in the sending unit, and the terminals seem to be in good condition. I’m going to clean everything using sensitive electronic cleaner, get rid of the old connections and recrimp it myself and shrink wrap it. I’ll repeat my troubleshooting method to see if I can replicate the problem afterwards.
Update: I think I found the root of the problem. Posting for anyone else who may have similar issues. These are the female terminals that pin into the blue connector on the sending unit. I already installed new butt connectors and continued to have the same issue. Noticed the connection issue was right at the blue connector. Depinned the female terminals and noticed the clearance on the lead wire is much greater and I believe that is what’s causing the connectivity issue
FYI if you use some sort of material in the gas tank it HAS TO BE RATED FOR GAS SUBMERSION. You mentioned heat shrink, a lot of that isn't rated to be submerged in gas, it will turn into goo.
The crimp connectors that come with the Walbro are rated for submersion, may be worth finding some new ones to re-do that electrical connection. Sounds like the previous owner just didn't get a good crimp going.
Regardless, glad you stuck with it and found the root of the problem! Now you know you can fix it right and don't have to worry.
Thanks for the heads up. I did get crimp connectors that were rated for fuel. I also put about 150 miles on the car yesterday and did not have any issues related to the fuel pump cutting out. So far so good.
08-10-21, 09:45 AM
