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jsymonds Reader
6/22/15 11:13 p.m.

I get one more day to work on this car before I have to wait for three weeks. Looking for ideas and things to test tomorrow! Here goes:

Background: I just picked up my 5th Miata in Milwaukee, OR. '96, 62k miles, great cosmetically except for the chipped up hardtop.

The rub: the PO, who seemed like an upstanding guy, parked it under a tree about two years ago when it started making noises "from around the valve cover". I guessed this was classic HLA noise. It also threw a code at some point before that due to an exhaust malfunction of some sort. Oh, and it has an aftermarket alarm/starter kill system. Too bad.

Since picking it up, I have replaced the usual tune-up bits. Battery, plugs, wires, cooling hoses, radiator, engine oil, coolant, trans fluid so far. Had most of it just lying around from the previous cars. Have a timing belt kit on hand, but I'm working a friends house and prefer to get into that in the comfort of my own garage.

However, when I went to crank it (after a failed "oops, unplugged wires" attempts) it started with a hesitation, then idled okay for about three or four seconds, and died. Cranking again immediately afterwards got no firing. If I wait maybe 30 seconds, it will repeat the 3 second idle and death.

Here are the tests I've done:

  • Adding some right pedal seems to kill it immediately.

  • Google thought it might be MAF-related. I put in a junkyard one, no dice. Wire going to it has power.

  • There is some kind of signal coming from the IG- diagnostic port under the hood, which should reflect engine RPM. It is steady 12V with the engine off, and the AC frequency seems correlated to engine speed. (It's an AC signal, right?)

  • Pulled OBDII codes (thanks to Baxter's Auto Parts for letting me borrow their tool!) Got codes for the problems I caused by forgetting to plug things in (MAF, air temp, and CAS sensors), and what I believe are old ones from the Beforetimes (exhaust pressure). Cleared the codes, tried to run it a few more times, no new codes. Not sure if that means there aren't any, or it hasn't run long enough to throw them.

  • I did not test the spark directly, but had a timing light hooked up to each wire. During the 3 second run it fires normally, but during the no-luck cranking it is generally dark until I let go of the key, followed by two blinks as it turns over the final couple of turns. Is this suspicious?

Now, the tank is full, and the gas is at least two years old. The gas cap was in sorry shape (I think a chef would call it "blackened with tree crud", and perhaps a little loose). I don't know if gas goes bad, but if it could, this tank would be a candidate. I poured in the fuel additives I had on hand hoping for magic (a bottle of Techron and half a bottle of Heet), but no such luck.

Could these symptoms be caused by a clogged fuel filter? I have purchased one hoping that it is.

Any other ideas about what it might be? What should I be testing next? (Thanks!)

bgkast GRM+ Memberand UberDork
6/22/15 11:17 p.m.

Fuel pump? That's just how the Saab I just resurrected acted, and the pump was dead.

Be methodical. Check for spark (pull a plug wire, put on a spare plug, found it and crank while watching for spark), check for fuel pressure, check compression.

dean1484 GRM+ Memberand MegaDork
6/22/15 11:26 p.m.

Try a blast of starting fluid and see if it kicks. If you can start it on that I would investigate the fuel supply more.

jsymonds Reader
6/23/15 1:26 a.m.

bgkast, I forgot to include that I tested the fuel pump relay with the jumper in the diagnostic port. It sounded healthy, but I don't have a fuel pressure gauge, and neither did the nearby parts store. I can try the sparkplug test. I thought the timing light should be sufficient, but that might give me a better idea of how healthy it is.

Good idea with the starting fluid, I had forgotten that stuff exists! That's quick and easy.

moparman76_69 UltraDork
6/23/15 4:52 a.m.

Have you completely disabled the aftermarket immobilizer?

MrJoshua PowerDork
6/23/15 5:21 a.m.

It sounds like you are getting fuel pump signal with the key but no signal to stay on from the MAF. Have you tried starting with a fuel pump jumper wire installed?

Knurled UltimaDork
6/23/15 5:45 a.m.

Or just see if it runs on carb cleaner. You're missing at least one of the four main food groups (compression, timing, fuel, spark) and fuel is the easiest one to isolate.

Runs for a couple seconds then quits, then needs time to relax, then runs for a couple seconds then quits is ALSO a symptom of a heavy exhaust restriction. It will run until it chokes on its own waste then will quit, then nothing until given time for the exhaust to dissipate.

But first, will it run on carb cleaner? It'll be fine if you just pull the inlet duct off of the throttle body, you're going to be feeding it the fuel so no need for the computer to measure air.

Flight Service
Flight Service MegaDork
6/23/15 5:50 a.m.

Take the fuel line off and run it from a bucket. That will take the back half of the fuel system off the list

Tyler H
Tyler H GRM+ Memberand SuperDork
6/23/15 6:02 a.m.

In reply to Flight Service:

Run it into a couple of 5gal fuel jugs and take care of the stale fuel issue, too.

Dusterbd13 UltraDork
6/23/15 6:34 a.m.

Security immobilizer. Disable the aftermarket stuff.

wvumtnbkr GRM+ Memberand SuperDork
6/23/15 7:12 a.m.

I was thinking exhaust too. Can you see if the cat is clogged? Just unbolt the exhaust at the cat and see if it runs.

TGMF New Reader
6/23/15 7:19 a.m.

Agree with the last few guys.....Fuel does degrade, and actually pretty quickly. 2 years is a long long time to store fuel. Disconnect fuel line at engine, run it to a bucket, close the fuel pump relay and get rid of all that old fuel. Should be a good strong stream of fuel coming out of the hose. If not, investigate the pump.

jsymonds Reader
6/23/15 8:53 a.m.

Great ideas, guys!

I was hoping that "bad gas" was something of an urban legend...I am not sure how to dispose of it, and I am not looking forward to storing ten gallons of this stuff in my tiny garage. Of course, that doesn't change the truth of the matter, but hopefully if it runs for 3 seconds it's good enough to keep it going if there are no other issues...right?

As for the alarm, I definitely plan to get rid of it, but I am afraid to do so in this temporary workspace. One look under the dash convinced me it was going to have a lot in common with bomb defusal, and at this point I think I have a 50/50 shot (optimistically) at breaking something that wasn't broke. And I like circuits. Besides, careful reading of the user's manual (what has become of me??) tells me that the system only cuts off the starter motor, and should never be able to interrupt a running car. Should.

Here's the plan I've cobbled together from these suggestions, prioritized by how much of a pain they are:

  • See if it will run with fuel pump jumpered. If so, sounds electrical? If not:
  • See if it will run on carb cleaner. If so, I like my clogged filter theory, but otherwise it may be bad fuel/juju. If not:
  • Test spark for real. If it looks fine:
  • See if it will run with exhaust unbolted at the cat. If not:
  • Shotgun time...I have a spare coil pack, I can throw that at it. If it does nothing:
  • Maybe change fuel filter and the gas just in case the carb cleaner test missed it. If not:
  • Janky alarm wiring? Something else was chewed on? Maybe the CAS is not really working like it seems? Hoping I don't get to this bullet point.
jsymonds Reader
6/23/15 9:04 a.m.

Forgot a thing: I am hoping that running for 3 seconds is also a sufficient compression test that I don't have to run one of those, either. Would be something I circle back to if all else fails.

BoxheadTim GRM+ Memberand UltimaDork
6/23/15 9:37 a.m.

It has enough compression to start, so I wouldn't worry about that. I also wouldn't shotgun parts at it (yet).

At this point in time, this sounds fuel related to me. I'd change the fuel filter first, see if that changes things. If it doesn't, I'd pull the cat and see if that changes things other than waking up everybody in the neighbourhood .

I've got a bike project at the moment that stood much longer than your Answer with old gas in it. That needed a new fuel pump and a good scrubbing of the inside of the tank. Bad gas is unfortunately not a myth.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
6/23/15 11:53 a.m.

After a couple of years, it's possible the injectors are all gummed up with bad fuel. Seen that on a Miata that sat for about two years. I'd go this route:

  • jumper the fuel pump. If that solves it, you've got a bad wire going to the MAF. This is common with the 1.6 cars, not so much on a 1.8.
  • check the fuel pressure. It's much easier than throwing parts at it.
  • de-alarm the car. Alarms make cars not work by design, and they're installed by minimum wage high school kids.
WonkoTheSane GRM+ Memberand Reader
6/23/15 12:02 p.m.

When the MAF on my Rx-7 died, it would very consistently run for 3 seconds and then die. I mean, there was no "cool down" period or anything. Jumper the fuel pump, but I'm throwing in for that not fixing your problem.

I second the cat imploding on itself and blocking the exhaust. Disconnect it at the cat and see if it runs.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
6/23/15 12:06 p.m.

Yeah, there's a "keepalive" signal from the MAF that tells the ECU the engine is running. Otherwise the ECU cuts the fuel pump off.

Knurled UltimaDork
6/23/15 12:07 p.m.

Seeing if it runs on carb cleaner is less work than any of those and it will tell you right away if it is a fuel issue or not.

Just sayin'.

dean1484 GRM+ Memberand MegaDork
6/23/15 12:09 p.m.
Knurled wrote: Seeing if it runs on carb cleaner is less work than any of those and it will tell you right away if it is a fuel issue or not. Just sayin'.


Tyler H
Tyler H GRM+ Memberand SuperDork
6/23/15 12:32 p.m.

When it runs longer than 3 seconds, you can blip the throttle and eject the chipmunks, mouse nests and cache of hickory nuts and acorns, right out the tail pipe. Been there, done that.

Kenny_McCormic PowerDork
6/23/15 1:10 p.m.

You can get rid of stale gas by running it in an old flathead lawnmower (they don't mind it one bit) or a gallon at a time into a car.

I don't like trying to run it on carb cleaner/ether/whatever, I keep a spray bottle of 2 stroke mix around for that. If it won't run on gasoline, something else is wrong.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
6/23/15 1:18 p.m.
Knurled wrote: Seeing if it runs on carb cleaner is less work than any of those and it will tell you right away if it is a fuel issue or not. Just sayin'.

Not really - you'd have to get the carb cleaner into the intake while retaining the MAF, while jumping the fuel pump is done with a paperclip in the diagnostic connector Jump FP to GND. The fact that it will start says that at least some fuel is getting through.

tr8todd Dork
6/23/15 1:32 p.m.

Did you check to see if the exhaust or cat was clogged by rodent debris? Just had a buddy pick up a TR7 that was doing the same thing. Turned out to be acorns in the cat. I use to work nights with another car guy, and we were constantly playing practical jokes on each other. One night I restricted his exhaust down to a 1/2" piece of EMT tubing. His Blazer started and idled fine, but as soon as he went to drive away, the exhaust pressure would build up and the engine would stall. He'd get maybe 100 to 200 yards and have to start the engine again. We worked nights and it was still dark out when we left. Took him 45 minutes to drive the usual 10 minute drive. I called him the next afternoon and let him know what was wrong with his truck.

Knurled UltimaDork
6/23/15 4:33 p.m.
Keith Tanner wrote:
Knurled wrote: Seeing if it runs on carb cleaner is less work than any of those and it will tell you right away if it is a fuel issue or not. Just sayin'.
Not really - you'd have to get the carb cleaner into the intake while retaining the MAF, while jumping the fuel pump is done with a paperclip in the diagnostic connector

Why? You'll be running it on carb cleaner. If you can run the engine by Manual Digital Fuel Injection, it's not an exhaust or ignition or compression problem and you can focus on fuel.

I've moved cars with dead fuel pumps by walking next to it with a can of carb cleaner while someone else drove. Pushing sucks

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