robertsmau

2001 Boxster, 94000 miles, 5sp

Car ran fine and drove to the gas station for a fill and then wouldn't start again. Everything electronic works, no check engine light, and the motor turns over but won't fire. It seems that there's no compression since the motor turns fast (I can smell some gas in the oil). I'm suspecting something serious but I don't know these cars very well. I'm interesting in hearing theories (timing chain, rings..) and developing the right order in which to start to check things.

I did a search but couldn't find any posting with a similar problem. I can hear the clutch switch and it turns over so I'm guessing the ignition is fine.

Macster

Not rings. Not timing chain.

Most likely the problem is the fuel pump, with the fuel pump relay a close second.

(Assuming you didnt' fill the car's gas tank with diesel.)

Gas smell from the oil is normal.

If the fuel pump is not working, then after or during cranking (having someone else crank the engine) you should not smell much if any gasoline smell at the exhaust. Don't burn the starter up though.

You can bypass the fuel pump relay, bridge some connections. Or you can buy a new fuel pump relay. They're not that expensive.

I don't have the steps handy to bridge the relay. When my 02 exhibited similar behavior I borrowed a fuel pump relay bypass from my local dealer's Porsche tech to eliminate the fuel pump relay and "confirm" it no start was the fuel pump.

Took the car to the dealer and the tech disconnected the battery and removed it, then exposed the fuel pump connectors and put shop 12V to the fuel pump.

The fuel pump did not run.

He removed the fuel pump, replaced it with a new one, and engine fired right up after everything reassembled.

Fuel pump in my 02 only lasted nearly 230K miles...

Sincerely,

Macster.

robertsmau

That's good news, although I kinda wanted a bad motor to do a swap. One question, why would a non-functioning fuel pump make the engine feel like no compression?

Macster

Your imagination fueled with a bit of (understandable) anxiety?

Seriously, the engine sounds like it has no compression cause it doesn't fire right up. You're hearing the engine under different circumstances than you've ever heard it before.

Now I'm not at the car so I can't hear the engine and make a judgement. I'm just thinking, under what circumstances can an engine lose compression from the time it is shut off 'til the time the gas tank is filled with gas and then restarted, say in the span of 5 minutes?

Unless someone stole the engine's spark plugs while you were in getting free coffee refill or a snack there ain't no way.

Rule is when you hear hoofbeats think horses not zebras. ('course someone will ask: "What if you live in Africa?")

The engine cranks but doesn't start, doesn't make any scary noises, cases intact, engine spins good. Fuel pump. I'd at least eliminate that possibility before I dug any further.

However, there is the remote possibility a camchain (anyone of the several: crank to intermediate shaft (the "biggie"; intermediate to one of the exhaust cams; or one of the exhaust cam to intake cam chains (which also have a variable timing mechanism present) skipped or jumped a tooth and the valve timing is off and the engine really has no compression, or less compression than normal because the valves are now out time.

Just in case, you might want to curtail engine cranking until you have checked the fuel pump and relay.

If you find the fuel pump ok, the fuel pump relay ok, the pump delivers good pressure/flow (no blocked fuel filter or pinched fuel line) then you might want to look elsewhere. Then the cause of the symptom becomes possibly more sinister.

Sincerely,

Macster.

Arick

Hi to both of you,
When my car run's I can hear the fuel pump running when I am beside the fuel lid. Macster, can we normally hear the pump when we place the ignition key to on? or it will go with the starter? Maybe this could help finding out if it is functioning?
Eric

Macster

Some model years Boxsters have a continuous fuel delivery system with the pump running alll the time the key is on and the excess fuel routed back to the tank.

If your car has this system then you should be able to turn the key on and hear the pump running. Your 01 must have this kind of fuel system. Thus, if you don't hear the fuel pump running either the fuel pump is bad or the fuel relay is bad.

My 02 has a returnless/on-demand system (and I believe newer models do too) that the pump only comes on when necessary.

Maybe the fuel pump runs for a moment when I first turn on the key after the car has sat overnight, cause I think I hear a faint humming for a moment or two that stops even before the 5 second oil level countdown has expired.

However, I don't think I've ever heard the fuel pump running in my 02 Boxster with the engine running.

Now the Porsche tech at the local dealer loaned me a fuel pump relay bridge connector -- you can buy one from the Porsche parts department -- to test the fuel pump and eliminate the fuel pump relay. Even with the relay bridge in place though the engine would crank but not fire and no gas smell at all so I suspected the fuel pump, which is what it turned out to be.

When I took the car in he exposed the fuel pump and connected shop 12V power to the fuel pump wiring connectors and verified 12V power present at the pump and yet even with the bridge the pump didn't come on at all. Fuel pump.

I asked him afterwards and the tech told me his experience is the pump just works until one day it doesn't.

I disassembled the thing but was not able to gain access to the innermost portion of the fuel pump's motor. As best as I could tell the pump looked ok. Just didn't work anymore.

Sincerely,

Macster.

robertsmau

I jumpered the relay, as per pelican, and I could hear the fuel pump running. Back to the relay and it doesn't run. I think I've found one of the problems so I need a new relay. Where can I get a layout of the relays? I think the fuel pump relay was out of place and I'd like to know what all of these are for.

robertsmau

Nevermind, I found a posting of a relay diagram. I've got a new relay on order and I'll post back the results later in the week when it shows up.

robertsmau

I pulled out my code reader last night and got a cam position senser bank 1 code. Is this a problem or just one of those secondary codes that get thrown when something else is wrong.

Macster

Hard to say but it is but it is a bit troubling.

One has to be very cautious, at least I feel I must, because not every no engine start symptom is a fuel pump or fuel pump relay.

Assuming the symptom is due to a fuel pump or relay and the engine cranking and possibly even engine running might exacrebate a serious but not yet fatal engine problem and a cam position sensor error bank 1 suggests a serious engine problem, although working from memory (always a bit risky) this error -- I'd like to know the exact error code) it is the sensor that is bad or causing the error not the reading it provides.

For instance there is an error code for camshaft position sensor 1 (or 2) signal implausible. Implausible suggests a bad sensor, a bad connection.

Then there are error codes for a reading below or above a limit. As with the implausible error codes the error codes associated with a reading above or below a limit can also be due to a bad sensor or a bad connection.

The proper steps would be to test the sensor and its wiring to verify the sensor and wiring are ok. I believe I have test steps though I'd need to error code to know which tests to list.

If not, then fix the problem and retest.

If you find the sensor and wiring ok and can find no other external source/reason for the error then the error can be internal which means it can be due to a camchain drive problem.

For possible fuel pump and fuel pump the diagnosis and repair are within the scope of a reasonably experienced and motiviated DIY'er.

Checking out camshaft position sensors takes it up a notch or two. But it ramps up the risks too. (There are risks associated with messing around with the fuel pump and fuel system too, mainly fire.) If the problem is internal to the engine then the risk is in working your way to this knowledge you can do more damage, possibly rendering a serious but fixable problem into a much more serious problem, maybe even destroying the engine.

You want to keep in mind when working on your car, any car, is to never put anyone's health, limb or life, including your own at risk. The next is to do no harm to the car.

You should consider at some point turning the car over to an expert/qualifed tech with the proper equipment to make the right diagnosis.

Sincerely,

Macster.

robertsmau

Macster, YOURE AWESOME!
Thanks for staying involved in my problems. I appreciate the advice but I've probably already done damage by tweaking this and that and then laying on the starter so we're beyond the "do no harm to the motor". I've got years of experience racing a FFR cobra so I can take care of a ford 302 with my eyes closed but these porsche motors are new to me and I don't know what to do with a sensor of any variety.

I got a P0343 and a P1397 code from the OBDII scanner.

Macster

Awesome I don't know. Just trying to help you out.

P0343 is Camshaft position sensor 1 - above limit.

P1397 is Camshaft position sensor 2 -- signal implausible; below limit; or above limit.

My Boxster OBDII references are at home and I'm at the office. (I can bring them in with me tomorrow. I have no 'net access at home, so all posting is done at the office now.)

I have my Turbo references handy though, maybe this will be of some help.

Diagnosis condition: engine running. Possible causes: short circuit to B+. If both CMP sensor signals are missing the start will take at least 10 seconds. For safety reasons the ignition timing is retarded.

I find the comment that if both sensor signals are missing -- and based on the error codes you supplied (though of course using my Turbo's OBDII reference) indicate both sensors (1 and 2) are not functioning properly -- that an engine start could be delayed by 10 seconds (at least). Obviously this 10 second (or more) delay could be mistaken for a non-functioning fuel pump or relay or something fuel related.

Now the document I has gets into very specific tests which may not have the same test points, etc., as your Boxster.

P1397. Diagnosis condition: engine running. Possible fault causes: loose contact; camshaft position sensor.

There's the same two sentences as I posted above: "If both CMP sensor signals are missing the start will take at least 10 seconds. For safety reasons the ignition timing is retarded."

Then there are again very specific tests for continuity, voltage and resistance.

Generally, if both sensors act up the source of the problem is a common fault. Unfortunately, the common link between these two sensors is the DME control module. But I'd not replace this until I was 100% sure it is the source of the problem/symptoms. But you have to know what you're doing to eliminate it. Some tests can put the DME at risk of static discharge and if one does this it can render a perfectly good DME bad.

I can't recall and don't have time to re-read the thread (at work and under time pressure, and my online time is monitored) but has the car been subjected to some water intrusion recently?

Let me see what my Boxster OBDII references have on these two error codes.

Sincerely,

Macster.

robertsmau

Thanks macster, I appreciate the extra diligence in helping me. It can wait until you have time to look up the Boxster references or the work emergency calms down.

Byprodriver

I don't think there is anything unique about the fuelpump relay, so you can switch it with a relay that is noncrucial to starting engine (headlights etc.) verify the relays are the same first by numbers on it & try starting engine.

robertsmau

I pulled the little green cam covers off the front of the motor and when I turn the motor over the cams don't move. I'm guessing that's a timing chain failure. Is this in interference motor? Does that mean the motor is shot?