txhokie4life

When should fuel pump relay be running?

keon, engine off as well as during starting

or only if CPS gives signal?

i was thinking its fuel injectors and spark controlled by cps (indirectly)

Btw, I’ve replaced cps

thx,

mike

Read the tea leaves wrong -- got a fuel pressure gauge on the car this morning.

No fuel pressure KEON or during Cranking.

I have a fuel bypass switch to empty the fuel tank.  With that switch i get nearly 4 bar.  So the fuel pump is good.

I was getting 12v on 30, 85, and 86 with 87 as 0v on the fuel pump relay.   But I was reading that incorrectly when I said things were good.

With the switch, I get ~12v on pin 87, and the fuel pump runs.

I ran out of time -- but now I need to go back and revisit some assumptions and revert back to the original DME and 

recollect some data.

Mike

All voltages on MFI/Start Lock/Ignition/Fuel Pump relays seem to make sense.

I also double checked all fuses, both in the kick panel and the main current distribution box.

Next is to check Fuel Pressure -- I didn't have the right connector for the kit I bought (murphy's law).

Will also check all crimped supply connections for a potential loose wire.  Didn't notice anything from before.

I have not swapped ignition switch yet.

But as I have assembled and disassembled over the debug, the starting even while jumping was getting worse, 

and not will not start at all -- but the car still cranks fine.

Mike

11 minutes ago, Ahsai said:

You may want to retrace your diagram above. Pin 85 of the ignition relay should be ground and pin 30 should be connected to fuse C2 directly. Fuel pump relay pin 86 should connect to start lock relay pin 86.

Correct -- I can't even read my own notes ?

Basically MFI closes (87) to supply power to the Start Lock, Ignition and Fuel Pump and other relay coils.

Of course it will be interesting to eventually figure out how my SPB is wired.  But at least I know how the system should work.

I will remove the diagram above and include this one -- so no one following is led astray.

Mike

Been crawling through the wiring diagrams.  This should be able to give me a game plan for probing.

I have access to the backside of the top 3 relays easy enough -- should be able to get

some good diagnostic information from them.

<corrected diagram below>

Thank you for your help -- I REALLY appreciate it.

I was fiddling around with those relays last night and noted one pin at 1V.

I was running a bit blind -- (knowledge wise) so I wasn't being meticulous about what was what -- next time I'll make some notes.

Believe the other pins were at 12v -- so that suggests it was energized -- now was that the DME or some wiring hack, who knows.

I'll add it to the list to confirm.

Mike

8 hours ago, Ahsai said:

Any error codes on the DME?

MAF having voltage means the DME has power. Is it easy yo get to any O2 sensor connector? If it is, you also want to check for +12v on any black wire. The coils and the injectors are on the same circuit.

 

Any tach needle bounce while cranking?

No codes

When I try to do live values, I was getting software errors and no valid values.

I did get basic info like running hours, overruns, DME #, etc.

I was unsuccessful to get to connect when it actually was running off the Cayenne -- I can try that again.

No tach bounce

I should be able to get to the o2 sensors.

Haven't confirmed Waekon, I'll try that as well.

Wish there was a LED or other indicator that said -- yes I am happy with the immob/key pill etc.

I'm waiting on the ignition switch.

Mike

Ok, 

got access to the maf

equiv of Keon-ignition off

have 12v and 5v ref

all 3 relays in the back are tested good

the two #1 & #2 are warm, and have 12v on 30 with relay out.

same for the black relay.

ordered ignition switch, should be here Thursday.

mike

That connector wouldn't budge -- thus I went to the forums and they suggested removing the MAF itself then accessing the clip that allows you to unplug ?

I did separately check the relays on a bench and they were fine -- but will check the MAF anyways.

M

Went to check Maf voltage but it had a security torx bolt ... really ?

Didnt have that kit with me

swapped dme/immob/key/ring/transponder. .. no change

checked spark with waekon... nada

ohmed out ignition switch... good, but not 50 which is start pin, however i suspect that’s intentional with push to start.

orderded an ignition switch anyways... they’re cheap and good to have as backup.

there is a 4 pin connector in the lights switch wiring bundle that’s dangling...  gray, yellow/white, brown, black/yellow if I remember right

cant find home for it, or in wiring diagrams

i do have supply voltage on the 40amp fuse

Mike

Will order that -- very nice (and a bit pricey - but worth it)

Brought a mechanic buddy of mine out to help -- basically reproduced and confirmed earlier findings.

We did attempt to check for spark -- his tool didn't fit well either -- thus ordering above.  It did not appear to have spark during cranking -- but we saw this we think

before it fired up by the other cars alternator route.

We did determine that if you remove the immobilizer -- this car still cranks (but does not fire).

We found where they stuffed the pill.  Thinking maybe the ignition switch or the little box that detects the rfid info is unhappy.

Will grab a spare and try that -- Also sourcing a dme/immob/pill to do a quick swap and test.

Mike

Thanks -- I will check the MAF VDD

I checked all relays and fuses last night -- all good.

I have 12.x V at the 40Amp fuse in the back.

I get a 430mv drop from battery terminal to starter post while cranking (which seems normal).

hoping to do a spark and fuel test tonite.

I spoke to the builders of the car -- they suggested that the IMMOB must be happy or there would be no cranking -- so it seems they didn't mess with that any.

Mike

23 hours ago, Ahsai said:

No tech bounce likely means the crank position sensor is bad but if that:s the case, jump start should not have helped. 

 

The immobilizer is likely fine because otherwise the DME won't allow the starter to crank at all (assume you did not rewire the starter circuit).

 

Have you checked for sparks and fuel pressure?

Changed cps... no delta

checked all fuses and relays

since it’s a race car with push to start, it might have been wired differently

tried to check spark but my test light didn’t fit, attempted wire to close to block, no spark, but that could be bad test setup

get fuel kit tomorrow and retry spark test

Spec boxster race car

push to start

will crank but not start

only time it starts is if jumped from another car w/o battery in system

3 different batteries

by passed kill switch, other switches

when it cranks, it’ll get to 35-40psi, so starter works.

duramatic talks to ecu 

immob looks fine (no corrosion)

supply and gnd connections look good (tight and clean)

if immob unhappy

what what would be symptoms?

No spark?  No fuel pump? No fuel injector?

does no tach bounce mean anything .. that’s a big hint on 944’s

thx,

mike

You should need nothing -- just hop in a drive her home.

The things that might go out are unlikely something packable.  WaterPump, Fuel Pump, AOS, a coil pack, Ignition Switch, Crank Position Sensor,

Anything else that might fail is unlikely to leave you stranded.  And even the above is highly unlikely.

Seriously, relays generally don't fail on these.

Make the drive and enjoy it!

Assuming you don’t want to tear down the engine and replace the bearings...

i would pull pull the plugs, pull the fuel pump

fuse put some diesel motor oil in the plug holes,

fill the engine with oil... and crank the engine first from the crank pulley bolt a few revolutions to make sure it turns freely

than I would crank it over with the starter until I built oil pressure.  Don’t crank for more than 30-60 sec so you don’t hurt the starter.

do this several times.

than drain the oil.

you should be able to refill, put the plugs and relay back in and then try it o start it.

flood water is probably better than an intermix, the cleaners and antifreeze itself are caustic to bearing material.

that shouldn’t be present in just flood waters

good luck,

mike

Unlikely to be bleeder valve.

it could have been your coolant cap was cross threaded and not on properly.

Other sources are WP or hoses, but they would likely show up when running unless it cooled enough your thermostat didn't open.  

The other source is a cracked expansion tank.

However, short of catastrophic, these usually appear as subtle losses of coolant.

Mike

There are orings on both sides of spark plug tubes.

oil leak can damage coil oaks over time.

brake pad sensors can be shorted, But that obviously bypasses their function.

Obviously check brake pads

Sensors are pretty cheap.  

16" tires are often cheaper :-)

mike

On one car there was a valve I had to replace under the intake (drivers side).  It would make noise around the gas cap area as well as throw the random CEL from time to time.

Take some painters tape and seal the hood to bumper crack and see if it goes away

if not do the same for convertible top seal

if either works could just be an alignment issue

mike

Check for air leak post MAF -- 

Had something similar and found that the jboot had worked its way loose.

Mike

What JFP said -- also make sure the CV Axle bolts are tightened (check torque specs).

Listen to Jake & JFP

Common as in, yes this a known failure behavior and the debris lines up with your cel.

if it was me I'd fix it ASAP... That debris is going everywhere.

furthermore, once the plastic is widdled away, that chain may start touching less forgiving surfaces.

at some point you could have a lot bigger problems to deal with.

things are not going to get better.

mike

No issues for 3 days -- thick we nailed it.

M

Fingers crossed -- we swapped fuel pumps and it appears to be happy.

Since it can be difficult to "recreate" the failure -- I'm still being somewhat reserved.

The interesting behavior is the Fuel Pressure readings always looked good.

The other issue was that the car only has 12.5K miles -- however -- it is not known just how long it sat when the engine suffered an IMS failure prior

to acquisition on my part.

The theory is that the pump was worn -- maybe due to bad gas -- and as it warmed -- it wouldn't always turn on -- however, when hot, there

might have been enough gas in the rail/lines/etc to fire the engine -- and once firing -- the pump worked fine (vacuum pull on fuel?, higher voltage after cranking?, DME sending more fuel request then just starting at idle?) -- at cold, pump worked fine.

Warm -- the fuel pressure had bled down, and the pump didn't run (or run well),  Allowing it to crank allowed it to build pressure or if that was not good enough -- blipping the throttle enticed the pump to work a little harder.  In the end -- who really knows....

So I'm hoping this is the issue -- and will guide some other poor schmuck who stumbles across this thread......

Mike