MK 2.5 not firing

Technical Area Engine, Transmission, Exhaust etc
2

So… today marks 2 months of my mk2.5 being off the road and unable to start. Let me take you back to beginning…

 …

Had it as my daily driver for about 2 years, always been a trouble free car.

One day I wake up decide to head off down the motorway to Donny to meet some mates. She starts up first time as usual no problem.

After about 15 mins of driving im doing 70 on the m18 when i notice shes died and im coasting. So i pull over to the hard shoulder and try starting her again. Nothing.

Cranks but just wont catch. I call the recovery guy out who proceeds to try starting her up and she fires up no problem, runs for about 30 seconds and then dies again and wont start back up.

 …

After being recovered back home he diagnosed it as undoubtedly the fuel pump. Now… I don’t recall ever listening myself to check if I could here the click and the hum of a working pump… I was too eager to replace it, wanting my car back so I could get to work. I decide to buy a working used pump with the rest of the system attached so I could just drop it straight in. So after a quick swap… nothing. Still not firing. 100% this pump is working though, I hear the hum and click and removing a fuel line and trying to start her up results in a gush of fuel spewing out.

 …

Since then I’ve checked for spark (all good) all the spark plugs look as they should. I’ve replaced the crank angle sensor after reading that might be the problem (Had the toothed wheel replaced previously after someone bent a tooth off when it was being serviced) I’ve replaced the cam angle sensor, again after reading that might be the issue.

Had a second mechanic out who found a MAF sensor error code and advised either vacuum leak, fuel starvation, or collapsed cat.

I replaced the MAF unit after that and although I didnt remove the exhaust i tapped the cat with a hammer to try and diagnose if there was any loose material in there and I just dont think there is. As far as a vacuum leak I’m just not sure where or how? It just seems to me like its a fuel issue.

…

Thing I’ve discovered that work… if I remove the air filter (got an aftermarket induction kit) and cover the intake with a bit of tape just right so there was a little bit of air still getting in. She’d fire up and run, quite badly but she runs. Also, if I remove the spark plugs and pour a tiny amount of fuel in each cylinder she starts up and runs for about 15 seconds.

Help me community! you’re my only hope!

3

Sorry to hear such a tale of woe.

It’s a MK2.5 , so onboard diagnostics. Have you used an OBD reader to interrogate your car’s diagnostics for error codes?

If I had to hazard a guess would say water ingress into passenger footwell and associated damage to ECU?    

4

As above,possibly water damage

5

 

I dont have an OBD reader myself but one of the guys that came and had a look did and said it just showed the MAF sensor error code

 

Oh weird, is water in the footwell a common thing? I’ll have a look tomorrow and see if I can see any signs although I imagine it would be pretty dry by now especially with the past few hot days

6

Imagination is a wonderful thing - regrettably reality does tend  to bite you on the bum:-)

Take my word for it water ingress into the passenger footwell is a distinct possibility and recent hot weather will only exacerbate the potential problem.

Take a wee  peak and report back.     

7

Hi, I’m new to the MX-5 Owners Club forum and just happened across your recent post.

I purchased a 2005 reg Mk2.5 last year and looking back at past servicing and repair docs I remember a similar fault having been repaired before my ownership.

I’ll just type the mechanics report verbatim in case it offers some insight into your problem.

"Investigated fault with engine not starting. Engine started and would not fault. Road tested, still not faulting. Engine eventually stopped and would not restart.

Carried out diagnostic code read. Two faults. 1x Camshaft position sensor. 1x Crankshaft sensor.

Inspected crankshaft sensor and found wiring to have chaffed through. Removed camshaft sensor and replaced with new.

Cleared all faults from memory. Road tested, all ok at time of test."

To my knowledge the car has not missed a beat since.

Hope this helps or at least allows you to rule out some possible causes.

8

 

Managed to have a look this evening, I should have taken a picture actually thinking about it… but it was spotless in there, no rust, muck, not a single mark its as it came out the factory. I water damage would probably be hard to visually see but I would have thought there would be at least some sign of residue from the water or something?

 

 

 

I’ve had a look for any damaged wires but I replaced the crankhaft sensor so the wires brand new on that, the old one wasnt damaged it either

 

I feel like it has to be something like this though, every post i read with all the same symptoms seems to be crank or cam sensor related.

Its so close to starting as well it doesnt feel like its something catastrophically wrong 

9

Have you checked the cam timing?

10

What a great technician write up, which garage is it from? A Mazda dealer?

 

11

 

Sorry for the noob question but how would I go about checking it?

I’ve read a post with very similar symptoms where it turned out the timing had completely gone out of whack. Is this something that can just happen?

12

It can happen, normally if something is loose behind the timing belt covers that gets picked up by the belt, a bolt or rubber seal maybe. You’lol need to remove the cam cover, set the engine to TDC and check the marks on the cam pulleys.