Necron

iTrader: (11)

This is on a 98 z28 m6

All the electronics still work fine. The car will be running smooth and the engine just dies after the car warms up for bit.

I thought it was the fuel pump because the pressure drops right off when the car dies, so I put a racetronix walbaro in and did the wire upgrade kit. Now the car has 62 pounds of pressure and it still does the same thing.

Now when the car dies it will crank but not start, but if you let it sit for a while it just fires right up again and runs great.

I've been told it could be a crank sensor, but I'm looking for some ideas of things to check. The car runs 100% fine then it just dies, its kinda odd.

Necron

iTrader: (11)

Any help or thoughts?

If anything is unclear please let me know.

I'm just looking for some direction to help me out.

99monguse

Sounds like a crank sensor

99monguse

Typically a crank sensor causes a shut down once the engine gets warm or hot and will allow a restart once it cools a bit.

Necron

iTrader: (11)

Would the Crank sensor issue cause the fuel pressure to drop as well?

99monguse

Not sure about the fuel pressure dropping with a bad crank sensor. Have you tried swapping the starter relay, they have been know to be bad too. I think the fan relay is the same as the starter relay. The GM part number for the Ignition relay is 12177236. I would try that first, then the crank sensor. Do you have any SES lights? Have you scanned the car? If all else fails, take the car to someone who has the ability to scan with a GOOD scanner, in real-time...equal to a dealers TECH2 to scan while it's acting up.

Necron

iTrader: (11)

No I haven't tried swamping the ignition relay, but I may give that a try tonight and just let it run to see if it happens. No I don't have any SES lights at all.

My last resort is to take it to a friends shop for a scanner, just trying to not have to make the trip out there with the car dying etc.

Necron

iTrader: (11)

Alright so update.

I switched the ignition relay and one of the fan relays and let the car idle. After a good 20 mins to a half hour the car did a few real quick heavy stalling. (Fuel Pressure dropped hard but recovered back.) Then the pessure was at around 40 instead of 62 and it slowly walked down to about 10 and the car only had enough pressure to idle (roughly) and it finally died.

Literally 5 mins after the fuel pressure was back up and the car was running fine again and it ran for another 10 mins no problem. Everything else on the car seems to still function when this happens.

It did this with the stock fuel pump and its doing the same thing now with the new racetronix.

Will a bad crankshaft sensor cause the fuel pressure to just die off like that when its failing?

Necron

iTrader: (11)

Does anyone know about the fuel pressure relation to a failing crankshaft sensor?

z-nasty28

when I get stumped I call the dealer, sometimes you can talk to the parts guys and get a hint over the phone for free

Forrest Finley

I too have the same problem. Did you ever figure out what the cause was. I have a 4.8 Bosch fuel pump, z06 cam, grantties maf. Car runs great for about 10 to 15 min and dies. Let it sit for 1 min fires back up no problem. Fuel pressure on start up is 60 psi. Fuel pressure does drop but I don't think it's the problem. Brand new crank position sensor 2 weeks ago because of start up issue. Ground wires all new. Right before it dies and you step on the gas and It falls on its face. IAT temp is at 113 and engine temp is 198. Any help would be great thanks

LS6427

iTrader: (2)

Crankshaft Position Sensor has NOTHING to do with fuel pressure or fueling. It also does not care if the engine is cold or hot.....if its going bad it will start and run great....then just shut off. Then it will immediately start back up no matter how hot it is....or it might not start for a few tries at the starter.

But....these PCMs and sensors are the Devil in disguise.

Go buy a new Crank Sensor.....drop the starter and put it in. If it fixes it...great. If not, pull it out and return it for a refund. Tell them it was the wrong one because the previous owner wired up a different type of sensor. Works every time.....

A bad Crank Sensor could possibly be going bad and it can send bad info to the PCM causing that crazy DEVIL to send strange signals somewhere else that can be causing this issue.

The Camshaft Position sensor does control fueling however.....could be that sensor doing something after it gets hot.

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Forrest Finley

Thanks for the quick response LS6427. When I get up I'm going to head straight to the gm dealer and buying both sensors. I want to drive my car. I've been building it for 3 years now and it's so close.

jrpimp00

iTrader: (17)

Did you change your filter too?

LS6427

iTrader: (2)

If its not the Crank Sensor...the dealer might not refund your money and take the part back. I would get one from Advance, PepBoys, etc......first see if it fixes the problem. Then if you want a AC Delco sensor....go get one from the dealer.

or order it from rockauto.com for probably half the price of the dealer......

Also...don't get a Cam Position sensor yet. Its not the Cam Sensor thats causing your problems.

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