miata help needed: Grassroots Motorsports forum: Grassroots Motorsports Magazine

Subscribe get a full year for only $23.95 Sample Free Test Drive—no strings attached

Dec. 30, 2009 4:30 p.m. 2.0dohc New Reader

ok so long story short, my trusty miata failed to start today after work.

it cranks, but doesn't fire

I have had it for close to a year and this is the first time it has let me down

should I be able to hear the fuel pump run when cranking? any ideas on what I should check? keep in mind that right now its sitting in a snow filled parking lot on base.
I took a quick look under the hood, no obvious problems, jiggled most wires/connectors, fiddled with the clutch switch bypass jumper...no luck

thanks
Dec. 30, 2009 4:34 p.m. Woody UltraDork

Check the fuel pump relay, near the passenger side front shock tower.
Dec. 30, 2009 4:34 p.m. mw Reader

I would pull the plugs and check for spark. If there's spark, likely you aren't getting fuel.
Dec. 30, 2009 4:38 p.m. ZOO Dork

I had a coil pack go bad -- intermittently the car wouldn't start. MW's suggestion of looking for spark is the best starting point.
Dec. 30, 2009 5:12 p.m. 2.0dohc New Reader

I was going to check for spark when I go back tomorrow, how would I go about checking the fuel pump relay?

anything else?
Dec. 30, 2009 5:26 p.m. Marty! The quicker picker-upper.... Reader

Check for spark. If you have spark try starting fluid. If car runs on ether then it's a fuel issue. As far as the relay goes, check to see if any other relays are the same number and swap (as long as it's not a critical relay, ecu, etc....) if not spend the $10 and try a new one. If relay doesn't solve problem then likely culprit is the fuel pump or wiring to fuel pump and/or relay.

If car has no spark then check coil. There are also a myriad of other things that will cause a no spark issue, but lets narrow it down to a spark/fuel/timing issue first.
Dec. 30, 2009 6:28 p.m. bluke1 New Reader

spark and the fp relay are 90% likely to be the problem. if those arent the problem get a code reader.
Dec. 30, 2009 6:58 p.m. 2.0dohc New Reader

Marty! The quicker picker-upper.... wrote: As far as the relay goes, check to see if any other relays are the same number and swap (as long as it's not a critical relay, ecu, etc....) if not spend the $10 and try a new one.

any idea where to find one for $10 if that's the problem? rock auto wants $77!!!!!!
Dec. 30, 2009 7:07 p.m. Marty! Beddar with Cheddar... HalfDork

Ahhhh, just looked at Autozone and theirs was $102. I had no idea that a Miata's FPR was that much (I've never had to replace the one in my Miata). I ASSumed that it would be in line with other relay costs.

Next guess would be junkyard or wait 'til some of the others chime in. I'm sure somebody here has bypassed one.
Dec. 31, 2009 12:14 a.m. Keith PowerDork

Let me guess, it was running just fine. You stopped the car and it refused to come back to life. We've been seeing a lot of failures of the main relay. Not the fuel pump relay. It's labeled different things on the fusebox lid depending on the year, but it's the big boy in the underhood box. You can pop the top off the relay with a bit of careful prying and get it to close with a bit of a squeeze (relays are mechanical, you'll see what's going on when you have it open). Once you get it closed, it should stay closed as long as the car is running.

If the relay's gone, you won't get fuel or spark as the ECU isn't waking up.

It's a big relay, so it is more expensive. I seem to recall prices more along the lines of $35 from Medcenter Mazda, though. There aren't any others in the car that are interchangeable as far as I know.
Dec. 31, 2009 5:48 a.m. 2.0dohc New Reader

Keith wrote:

Let me guess, it was running just fine. You stopped the car and it refused to come back to life.

Yup. Drove to work wensday morning ran fine, but not after working my 12 hour shift

Guess I should mention this is a 94 if it matters.

On a side note, on the way to work I almost ran over a deer. The road was so slick it fell down in front of me as it tried to run away .
Dec. 31, 2009 6:20 a.m. integraguy HalfDork

While the others here have made excellent points, don't completely disregard the battery as a possibility. I had the battery in my truck quit suddenly, though it was nearly 4 years old. It started the truck fine and got me to work but when I went to go to lunch....it was "suddenly" dead as a doornail. But then, I'm assuming you tried to jump it already and/or took a voltage read on the battery.

I had the main relay on my previos Civic die on me. Usually, but not always, it will "pretend" to die before actually giving up. Your Miata doesn't sound like it did that.
Dec. 31, 2009 9:33 a.m. joey48442 SuperDork

My uncles timing belt broke (actually lost some teeth) one morning when he went to start his car. Open the oil fill and make sure the cams are spining.

Joey
Dec. 31, 2009 12:53 p.m. Keith PowerDork

Based on the phone calls we get, most of the Miata ones don't give any warning. You just get a dead car one day.
Dec. 31, 2009 12:59 p.m. integraguy HalfDork

"Based on the phone calls we get, most of the Miata ones don't give any warning."

What "ones"? are you talking about?

BTW, aren't Miata BATTERIES supposedly on the small side?
Dec. 31, 2009 1:16 p.m. Keith PowerDork

Sorry, I should have quoted. Based on the phone calls we get, most Miata main relays don't give any warning.

I've not heard of a Miata battery failing like this. Usually they'll show signs of slow cranking before the ECU voltage drops too far down to wake up the computer. I can tell you that a 2000 Jeep Cherokee battery will fail in this manner, though.
Dec. 31, 2009 4:19 p.m. 2.0dohc New Reader

OK so after trouble shooting it for a while in the cold, I got her to run

main relay clicked, just to be sure I popped the cover and say it move spark is there fuel relay clicks, and there was power checked at the pump, its got power

But....when I check for continuity across the pump at the plug I get nothing, I get a reading on the fuel float pins but not the pump...so before I spend the $130 for a new pump I thought I would ask you guys.

Do I have a bad pump or at least a wire problem in the tank?
Dec. 31, 2009 8:00 p.m. 2.0dohc New Reader

I went ahead and picked up a new pump, and I get a reading across the terminals, so either the old pump is bad or some wires came off in tank.