aproo

Came in to do some maintenance work: replace new coils, new spark plugs, , serp belt, change new water pump and tensioner. After all these are done, my car can't start now. Mechanic is telling me it could be a starter problem. However my car was running fine before doing all these, how is that possible.

Someone can help please..?

Macster

What are the symptoms? Does the engine crank?

If the engine doesn't not crank... How long did it take you to do the work? If you leave a door or trunk open this can possibly drain the battery dead.

Did you disconnect the battery cables? Did you disconnect any wiring harness connectors while you working on the engine?

If the engine cranks but doesn't fire check the fuel pump fuse.

Sincerely,

Macster.

aproo

Thanks Macster.

The engine does crank but it does not fire up.

The whole job took approximately 2 days. We thought it was the battery as well, but we changed a new battery to see if that was the case. Alas no it wasn't.

I am pretty sure, the mechanic did not disconnect the battery cables when he was doing all these.

I will ask him to check the fuel pump later and see if that is the case. Why would the fuel pump fuse get affected? How do you tell if it is damaged?

Any other common known causes for this? I don't think it is the ignition coils or spark plugs as these are brand new. Its baffling because the car was driving fine until i did these maintenance works.

Cheers.

Macster

The last thing touched is the first thing suspected.

But in this case I don't think all coils were installed incorrectly, nor do I think all coils are bad. I hope the right coils (and plugs) were used.

The fuel pump fuse can fail at any time, though of course they fail rarely. But you want to eliminate the fuel pump fuse and relay. When my Boxster would crank but not fire I sort of suspected a fuel pump (172K miles on the original one) so I borrowed a fuel relay bridge from one of my local Porsche dealer mechanic and tested the fuel pump. It did not turn on even with the fuel pump replay bridge in place of the fuel pump relay. IIRC I used a spare fuse just in case the original pump fuse was bad. I didn't have a way to confirm the fuse was goo. Fortunately the fuse box contains several spares in IIRC the bottom row. The fuse box cover might have a diagram of where the spares are.

Anyhow, what might have happened is the fuel pump quit. Hey, it happens. Again with my Boxster I started the already warmed up engine and just moved the car back a few feet when the engine died. I cranked the engine again it caught then died. Then after this the engine would crank and crank (though don't overdo it or you'll possibly damage the starter (overheat it)) but not so much as even hint at wanting to run again. The fuel pump went from working just fine to not working at all in almost no time at all.

But check the fuse and relay and you can eliminate the fuel pump pretty quickly.

Just a thought but I read/hear there have been a lot of gas thefts lately. By chance someone siphon your car's gas tank dry?

Next up for suspicion is that in working on the car you jostled or somehow knocked a vital electrical connector loose. Maybe not all the way just enough to cause this symptom.

Which vital electrical connector/connection? Well, one that comes to mind is the one that connects the DME (via the engine wiring harness) to the crankshaft position sensor located at the back of the engine (at the transmission end) on one side, I think the passenger side of the engine but this is where my Boxster's sensor is (and I don't know for sure where my Turbo's sensor is located) so your car may have this sensor on the other side. But it has to be at the bellhousing end of the engine.

This sensor bolts to the engine block and the sensor extends into a hole in the engine block external webbing so the sensor's business end is positioned quite close to the flywheel. As the flywheel spins the sensor senses the passing of metal tabs these tabs extending at right angles to the flywheel's face.

These tabs whizzing by (in partnership with the gaps (some even, some not even)) create an electrical signal at the sensor that is fed to the DME and from this DME knows the speed of the engine and where each piston is in each cylinder.

From this info the DME determines when to trigger a fuel injector pulse and when to trigger a spark.

If the sensor is not working the DME will not trigger any fuel injector pulse so you won't smell gas at the exhaust pipe. It will not trigger spark either.

But the engine will crank. Just fine too.

So, you have to eliminate the crankshaft position sensor by verifying during the coil/plug R&R the sensor didn't have its connector partially loosened or the sensor wasn't hit by a wrench or an arm or something and knocked out of position. Even if the connector is not loose the sensor needs to be positioned 'just so' in order to work properly. So if it was bumped hard enough it may no longer be positioned properly.

Before you wrench on the sensor before you grab it to see if its loose you need to visually determine if the sensor is located properly. It may not be the sensor but if you go messing with it you can add to your problems.

Sincerely,

Macster.