Although I'm not totally finished with this yet, I just had to post this initially...

I'm in the process of fixing this, but I need to run out and get some connectors.
I'll do a full write-up on post it to my website soon...

My car had an intermittent loss-of-power just driving around.
I felt like a huge bump would cause the car to just lose power - it would barely idle and it burped and backfired if you got on the throttle more.

I also had a voltmeter installed to keep track of the voltage to the fuel pump...
It showed that the fuel pump was getting ONLY 8.0VDC at idle.
When boosting, the voltage would usually DROP down to 7.0VDC!
DOH!
This would explain why the EGT's was showing so high under boost!
The voltage would intermittently pop up to about 10VDC under boost - it is supposed to switch "high" when going into boost, but it would only do this maybe 1 out of 10 times.
So I figure ground was bad - I redid the ground wire, but this didn't help.
The added ground wire DID help a little when the fuel pump voltage did switch "high" (which was rarely) to 12.0VDC - which is still kinda low.

Okay, so today I had some free time, and I tore into my newly acquired FSM.
I checked the circuit opening relay under the steering column - it checked fine per specs.

I then tore into the fuel pump resistor relay...
The resistance looked okay, but the resistor itself (spec is 0.64-ohm with no deviation) was a bit high -> 1.0-ohm.
The resistor itself is stamped "0.64" on the side.

I decided to tear into the relay itself...
You can see from the pics itself, it's wasn't good...

I dunno how this happened, cause the relay has a rubber seal on it!
WTF!

 

Go get yourself a nice ACD part number 15-8571. I think the newer number is 15-50688.

 

Why don't you wire the fuel pump through a seperate dedicated relay that gets power directly from the battery? Fuel pumps are not happy with below 12volts. 13 is even better.

Andrew

 

How is a fuel pump not "happy"? It's just a freakin' electric motor.

Sorry for your situation ReTed, but I think this makes us humble rx-7 owners happy to know that stupid things like this and your door handle happen to even the experts!

 

Experts' cars are far from problem free. The difference is in their ability to quickly diagnose and fix the said problems.

 

That's a load of BS. The 2-speed system works fine, and most EFI cars have something like this. Removing it will simply result in richer low-load mixtures.

Ted, that's pretty weird. That must be one of the better protected relays in the engine bay. I had exactly the same thing happen to me auxilary e-fan relay. Its inards were a solid lump of rust. All the other relays around that one were fine.

What's interesting is that the relay must've failed during low-load driving. When the relay is off the resistor is bypassed. The ECU switches the relay on and this opens the NC contacts and diverts the voltage through the resistor. If the relay had failed when the engine wasn't running the pump would've always seen full voltage.

 

why go to all that trouble?

dont tell me that you of all people are using the stock ecu? if not just rewire the fuel pump with better wire to a dedicated relay. i used a 40A Bosch relay and 8ga amp wire. perfect voltage to the pump, all the time. im not screwing around with old crappy wiring to my fuel pump. fuel cut=bad.

note: if someone other than Ted reads this, do not take my advice unless you have an aftermarket EMS. the stock ecu needs the stock fuel pump relay.

pat

 

I was having the same fuel-cut feeling in my NA then finally I just could not get it started. After reading this thread I went out an pulled the fuel resistor and relay and looked inside the relay and it is just starting to rust in there. The contact portion of the relay was not rusted though, just the coil portion. Could this still be part of my problem? Can I just clean the rust off and try to seal it better, maybe with some RTV?

 

Do you think your boost-a-pump had anything to do with that Ted? Or are you not using that anymore, or were you not the one that even had that? God I can't keep up with people and their mods anymore!

 

oregon is the shiznit

 

RETed, I thought you were using a standalone of some type. Why use the stock fuel pump relay in that case?

 

Car is going to go E8 as soon as I get the go-ahead.
I was sitting on the fence on the E6X and decided to skip the E6X totally.
I was leaning toward the E6K until I heard Haltech was going to discontinue.
I almost got an E11 until the E8 was released...full sequential - yum!


-Ted

 

Yeah, it IS puzzling!
When I took the relay apart, it had a pretty snug rubber "insert", and I dunno how all the rust started forming!
I don't think the driving environment could've done this.
I CarFax'd my VIN a few years ago, and my car originally was bought in Colorado!

I've taken apart other relays, and rust and oxidation was basically nil.
I'm almost tempted to start pointing fingers are the 3rd party contract company that produced parts for Mazda???


Yeah, I was staring at the FSM, and you hit it right on the head.

This would explain why the voltage starts to drop when the engine goes into boost - FPR tightens and bumped up fuel pressure, and the fuel pump just barfs.

After thinking about it, this doesn't explain why the car would occasionally lose power - zero power / add more throttle and it pops and boost goes up but goes no where - almost like excessively retarded ignition timing.
If the relay stuck closed, then it would be at full voltage.
If the relay stuck open, then it would be at ~9.6VDC.
Maybe the relay was trying to switch between the two and made some nasty voltage ripples in the current? :P

I dunno - it's not worth it to me to go trying to figure this one out - the Haltech is around the corner, and I don't want to deal with this crap.

I just wanted to post the pics just as a data for everyone else to see...


-Ted

 

Yeah, that's the other variable.
That's another headache that kinda popped up recently.
My BAP got "flooded" and one edge was under 1" of water. :P
I've been trying to get a replacement for it.
As I've posted prior, I'm stuck in limbo due to the impending Haltech conversion.
This makes me lazy to take care of "small things".


-Ted

 

See prior replies.

Sorry for the late replies, but I thought I would have the time to port yesterday.
Figures that we had a scheduled outage at work yesterday, and we never got power until the end of the shift.

I do have notes for the colors codes so you can rewire the relay with any Bosch-type relay, and I have one more pic to upload.


-Ted

 

arent old cars fun!