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No power to red/white wire on plug on fuel pump. Fuel pump fuse is good, resistor ohms out at 7 ohm, fuel pump relay is good. I have power at the diagnostics plug.
But no power to the pump.
Some may remember me posting about the car just dying...no indication of anything, just running one minute and dead on the road the next. Immediately thought fuel pump so changed that, still no start (and the old pump ran fine when 12v put to it.
This one really has me stumped. I gave the car to my son a few years ago, and it is sitting dead at his condo, which he is moving from next week so...I need to figure this out. Last resort I will have it towed to the local Mazda dealer and be prepared to face the music.
Any ideas? I am going to jumper the fuel pump at the tank plug tomorrow by making a spice connection to the factory plug and supplying 12v to the red/white wire and grounding the black. There are (4) wires in that plug, the two large ones that I assume are for power, and two smaller ones that must be for some feedback system?
The resistor should be around 0.7 ohms not 7 (might be you made a typo?)
The other two wires on the plug are for fuel level sensor mechanism. W/R is what you need to measure the voltage on.
If you keep the fuel pump jumped from the diagnostics box, do you still get no voltage on W/R wire?
Point 7 ohms sorry for the typo. I'll run some more tests today. Everything I've checked including the fuel pump fuse in the box in the driver's footwell is good. I just don't have power at the fuel pump connector. Which begs the question of, what could have happened to make it die the way it did? I owned the car personally for over 20 years, did everything one could do insofar as Maintenance/repair including installing a new 'built' engine. There has to be something basic I am overlooking or perhaps as Redbul notes rodent damage? But to be running then stop, AND to now NOT have power at the pump. I assume that if I directly power the pump from another source (golf cart battery) running only to the red/white and black wires, leaving the other wires on the fuel pump alone and plugged in, it should start. I'll make sure I am getting fuel to the engine by pulling a line. But even if it does start this way, I am still faced with the problem.
Well...ran the fuel pump, confirmed it had flow to the engine, let it pump for 15 seconds or so, still no start. Did this multiple times. Checked spark...has spark. How the HELL if it has air, spark, and fuel is it not lighting off? Checked the codes, only one flashing ( 4 slow) was related to a purge solenoid.
Dumb question - any chance the plugs have gotten fouled? If you haven't checked them, you should to eliminate the possibility even though the symptoms make that unlikely to be the root cause of the issue.
I keep coming back to this: WHAT could have caused the car to shut down like it did? I know that the fuel pump is not getting power unless the FP and GND are jumpered...WHY? Is there something in the ECU that could have failed, but if so why so suddenly? Whatever caused the car to die is still in play. The instructions in the FSM when it comes to the condition of no power at the white/red wire is #7, "check the circuit opening relay and its circuits". Which I have done. Chasing my tail here. Why did the car shut down? It shut down because the power to the fuel pump was stopped....but why?
One possibility is some type of wiring failure. The original wiring harness is 30 years old. There is a fuel pump rewire mod that many of us have done years ago to increase the voltage at the pump. It sends a new 10-12 gauge wire from the pump to the battery area and then either bypassing the resistor, which I don't' recommend, directly to the main fuel pump relay or directly to the speed relay in the front fuse box, which preserves the resistance circuit. Also, a new wire is sent from the battery to the main fuel pump relay, bypassing the lower voltage burdened ignition power. Search the forum for a write up on it. I would at first just test the pump housing plastic connector (which sometimes melts from heat) and connections in the tank to the pump by running a 12 gauge wire, outside the car, directly from the battery to the pump + on the disconnected pump housing connector and a ground wire to the pump negative on the disconnected pump housing connector.
Mike
We spent 30 hours tryin gto get my care to fire after a flooding event. Finally figured it was bad gas.
Replaced the gas but the car was still flooding.
We figured not enough air was getting in, so we removed the ISC and let the engine suck in air post the TPS and ISC, while a tech moderated the air flow with his hand (over the iSC port).
This did the trick.
Car started fine after that, but I got my fuel injectors refurbished and a new fuel filter put in regardless.
Edited: Jumping GND and F/P bypasses the signal ground from PCM's 1T pin to fuel pump relay (L/B wire). I'd check the continuity between F/P on diagnostics box and 1T pin on the connector to PCM.
Automatic transmission. Okay...now I am confusing myself. In the box there's the EGI relay and the circuit opening relay...is there a separate relay for the fuel pump? This picture seems to indicate it...item 14.
Ok, I have been confusing the 'circuit opening relay' (green one) with the fuel pump one. Guess I need to test the fuel pump relay. I assume the same way as the circuit opening? Power it up and test for continuity across the other two pins?
The wiring related to the fuel pump runs all over the engine bay, back and forth through the Front harness and then through a number of other harnesses. Room for trouble everywhere.
Check in your wheelwells to see if you have worn through the liner and then the Front harness If things suddenly happened, maybe you exposed some wires.
(This exactly happened to my friend who has had his car for 20 years and had no reason to suspect a "rub-through".. He had no idea when it happened.
Is your relay box intact? Getting water in there will get water into your front harness.
What ECU do you have and what are the injector sizes? ECU failure is possible, before you get too deep I'd swap ECU's to see if it will start and idle if you have access to a spare.
Disconnect the 22 pin connector from the ECU, and check continuity between 1T pin and F/P on the diagnostics. Here is 1T pin after you disconnect the 22 pin connector:
If you get good continuity, then as mentioned above swap to another ECU and test it.
I’d yank that purple motor eater and install a stock ECU or a PFC to see if it runs.
lol...yeah, they DID have a reputation! To be clear, I am NOT running the PFS box. It is a "piggyback" unit. I'll do the check armans suggested next time I work on the car.
I took the car to the local Mazda dealership. Prior to doing so, I called and asked them if they had anyone familiar with the 13BREW engine, the Service Manager huffed, "Sir! ALL of our technicians are Mazda Certified and are QUITE familiar with the rotary engine!"
I replied okay, just checking...I need a proper diagnosis ASAP.
My son takes over the task of interaction with the service department.
On day one they call him and say, "It appears to be insufficient voltage going to the starter." You can't make this **** up. So my son takes them through the likelihood of the battery being drained due to all the testing he and I had been doing, and he reminded them that we had told them the engine was turning over fine and fast, as we had a booster on it the whole time as well as a new battery.
Oh, they reply...let us look some more.
They just called him a while ago and said, "We think it is a total loss of compression."
Now, I remember back several years ago when the engine 'blew', it lost apex and side seals from several rotor faces, but would still run, albeit EXTREMELY roughly.
The car SOUNDS like it has compression, though admittedly I didn't do a compression test, didn't even pull a plug out. I suppose it COULD be the issue, but the way the car died according to my son sure doesn't support that. He wasn't boosting it, just driving down the road, and it just shut off.
My confidence in the dealership's technicians is not high, let's just put it that way.
08-09-24, 04:30 PM
