Fresh Rebuild Started fine but now no spark
 

I just did a fresh rebuild and it started up perfectly fine. The map sensor was out of alignment so it jumped to 3K and stayed there for the initial startup. The only other issues was a CEL for a knock sensor that may have been either due to a bad sensor or faulty wiring. I tuned the map sensor to within range and it was running perfectly with an idle around 1k while I was still dialing it in. The throttle was responsive and seemed like everything was going good until all of a sudden it just stalled out. At this point there might have been a combined runtime of about 45 mins with a couple start/stops.

I can get to start but it takes a bit of effort and it sounds like it's not firing on all sides. I can smell fuel and the compression chugs sound good (no galloping). I checked for spark and there is spark on the trailing coils but nothing on the leading. I swapped in a new used Leading coil (Terminals measured out to be just under 1 ohm) and it still wouldn't start. However during this attempt I actually noticed one of the terminal wire (the Y/L one not the B/R) start smoking through the insulation/tape at the. Can anybody offer some help on this?

Check continuity on the Y/L wire between the coil and the igniter. Also continuity between Y/L and ground. I'm no expert, but usually when wires burn up theres a short somewhere.

https://cimg5.ibsrv.net/gimg/www.rx7...ca5cd3e22b.png

Continuity is good between coil and igniter. Also good between coil and ground and between igniter and ground.

Also swapped igniter with my other running fd and it works fine.

Sorry, I meant TPS not Map sensor. My head is upside down from all this.

I meant check continuity between YL and ground. I don't think it should be in the same circuit, or am I wrong?

You may also have a short between the shield and the YL wire.

Thank you! Thank you! Thank you!

It turns out the insulation on the YL wire broke under the shield and was shorting out. I wasn't even aware this was a shield wire. I thought the PO had spliced in newer/thicker wire and that's why it was the different gray color. I trimmed it and soldered in a new section and now have leading spark again.

However the plugs were now fouled and needed to be swapped out. There still wasn't enough fuel to start so I had to run a bypass on the fuel return into a bucket to monitor the fuel flow. At first there was nothing coming out until I kinked the line a few times to let the pressure build up (grounded the F/P and GND terminals). I tried shocking the line to clear any clogs by kinking and unkinking the hose a few times. Eventually I got a small trickle out of the return line and let it run out for a little bit.

This was enough to get the car to start. It idled fine, got up to and maintained temp, and hot started a couple times. I probably ran it for at least 30-40 minutes on and off. I shut it off for about 20 minutes and when I came back to it wouldn't start again. I tried again this morning with a completely cold engine and still no start.

My thoughts:

1) Clogged fuel filter? The car sat for 7-8 years with a full tank of gas. When I went to drain it there was only about 2 gallons left in the tank.

2) Should the flow through the fuel return be more than a slight trickle? It really isn't much more than a pee stream (sorry I coultn't think of anything else to compare it to).

3) I did notice another electrical gremlin. With the key in the on position the radiator fans turn on. The climate controls are off, AC is off, headlights are off and the car is cold. Shouldn't the fans only come on under a combo of the mentioned conditions? I noticed this yesterday but eventually when the car actually started the fans did what they were supposed to (not be on).

1. Change the fuel filter. It's cheap.

2. Yes

3. Hard to say there, but I'd guess one of two things. Either the P.O. hotwired the fans to run all the time, or he's using thermoswitchs in the radiator to trigger the fans.

If you have 8 yr old gas...

- Get rid of the old gas.
- Have your injectors serviced
- New fuel filter
- Check/replace the fuel sock
- A new fuel pump probably wound't hurt (upgarde to a Supra pump)

The old gas has already been drained. I refilled it with about 10 gallons of fresh gas and let the pump push about a gallon through the system and out the return line into a bucket. I have a new fuel filter and haven't put it in yet. I will try swapping that out next.

In my experience, the stock ecu turns on the cooling fans when something isn't plugged in or a circuit is missing. Double check all of your wiring as they shouldn't be running. Even on the simplified sequential, the fans shouldn't be on.

It took a couple cranks but it ended up starting yesterday evening. It idles fine so I left it to run. It probably ran for about 10 minutes then stalled out at some point while I was inside the house. Wouldn't restart again after that.

I installed a cheapo Fuel Pressure Regulator on the return line just to monitor the pressure. It read about 42 psi with the pump on. It doesn't get any higher when I adjust it so am I assuming correctly that it won't exceed what the OEM FPR is set at?

The plan this weekend is to get the new Fuel Filter on, a new Fuel Pump sock and possibly drop the tank to clean it. Is there a chance the fresh 10 gallons of gas I added could now have been contaminated by the residual gunk in the tank from the old gas?

looks like you have decent fuel pressure (think the FSM lists ~47), so if you have a fuel issue, it could be your injectors. A new filter won't hurt, but doubt that will fix your situation if you are seeing good pressure. Another possibility is the tune. It sounds like it's dying when it gets up to temp. Are you running an aftermarket ECU?

So this weekend I replaced the fuel filter (PO had actually bypassed the fuel filter) and the fuel pump strainer. I dropped the tank and rinsed it out a couple times with the newish but possibly contaminated gas that I drained. I also sprayed the inside down with B-12 and that really loosened up some of the gunk. The gunk looked like pollen and turned the B-12/gas mixture yellow but overall the tank really wasn't that bad. There wasn't any sludge or an overabundance of grit, anyways. I poured a little bit of Techron into the feed line at the fuel rail and let it sit overnight (hopefully this helps with any unfiltered accumulation at the injectors).

Fresh gas went in this morning and I let the Fuel Pump run for a few minutes to clear and cycle the lines. It took a couple cranks but fired up eventually. It ran until it just beyond operating temp (20-25 mins) then stalled out again with no warning. It wouldn't start again after that. I pulled the plugs and they were fouled so I replaced with a brand new set of platinums which got to car to fire right up. What bothers me is how could it be running and then just lose spark and foul up?

The new plugs ran for a few minutes and then stalled out again just past operating temp. This time I noticed that it died when the fans came on (FYI the AC and headlights were already on so I'm guessing the Thermosensor must have triggered fan stage 3?). It took some effort but the car restarted only this time it sounded like it was running on one rotor. The tailpipe was spitting black smoke and my eyes were burning. Full throttle maxed out revs at about 3K. I killed it and restarted it about 2-3 more times with the same result until eventually I got it to start and running on two rotors again. The throttle was responsive and the idle was smooth at about 1,200. I went to the front of the car and a few minutes later I hear a relay click and then the car stalls again. It restarts on one rotor again, then two and then stalls. At this point I call it quits for the day.

I am completely stuck right now. One of the joys of piecing back a car that comes in mostly on a utility trailer.

With all that gunk and bad gas, I bet you one of even a few of your fuel injectors are not working well or may be stuck open. That would foul your plugs due to overly rich conditions. You unfortunately may need to pull the injectors and have them cleaned. Did you have them cleaned following the rebuild? Alternately, you could try highly concentrated fuel injector cleaner and try to clean them that way, although if stuck open it might not help.
Mike

Two nights ago the car started, warmed up then died. It immediately restarted which it never did before without issues and remained running for about 45 minutes that night. I even cycled in a few hot starts with no issues. Given its better running state I poured in half a bottle of Techron into the gas tank and slurped up about 3 oz of seafoam through the intake manifold.

Yesterday it started fine first thing in the morning for about 15 minutes and then hot started fine. In the afternoon I started it and ran it for about 3 hours (couple on/off cycles) while I bolted on the fenders/bumper and other miscellaneous stuff. Things are starting to look promising and Mikejokovich’s theory about a sticky injector might make sense. I’m guessing maybe it finally worked itself loose.

As of right now the car idles fine and is lower at about 1,000. The car does hunt a little bit (~150-200 rpm’s) when you try to hold at any RPM above idling. There is a CEL for a knock sensor and both sensors I’ve tried doesn’t get it to go away. I am assuming faulty wiring and will try rewiring it direct to the ECU. It is off to the DMV today and a possible road test in the next day or two. Fingers crossed.

Glad to hear it. I am sure your injectors were gummed up.
Mike

Nice.

Got the car on it's maiden voyage yesterday. I logged about 25 miles and the car still had the CEL for the knock sensor so I babied it quite a bit. Overall it drove pretty good - shifted nice and the brakes/suspension were still solid.

There is still a warning buzzer that stayed on constantly. I don't think it's the coolant as the light is not on. The buzzer seems to come on with the CEL and stays on. I tried grounding the coolant level sensor too and it still stayed on.

Anyways here are some pics from the way it came in to how it sits now:

https://cimg8.ibsrv.net/gimg/www.rx7...5e6b055283.jpg
https://cimg1.ibsrv.net/gimg/www.rx7...8f6070f586.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...6c1cd2c202.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...a1a7231706.jpg
https://cimg7.ibsrv.net/gimg/www.rx7...9e85cd93ce.jpg