Another no start issue

964 T #304 · 09-14-2009, 09:35 AM

On a c2 turbo could the security system keep the pumps from coming on with the Ing. key. I can pull the relay and hook up pressure gage to the digital WUR and fun my remote starter button to terminal #30 which has 12 volts and the other leg to terminal #87 and when I press the button I have 95lb. press. with gage closed and about 62lb. with it open with Ing. key off. I can install the fuel pump relay and turn the key on and I don't have any press. reading. I have replaced the relay with the one from my fog lites (which has same pt#) and I have no readings with key on . I have 12.83 volts @terminal #30 with key off or on and 12.83 volts @ terminal #86 with key on coming from air bag module. Terminal #85 is supposed to be a ground from turbo control unit but if I test between terminal #30 or # 86 to terminal 85#,the turbo control unit I only read .85 volts. Does the engine have to be running for it to be a total ground . This whole issue started when I let the battery get low and put a charger on it and had it on 40 amp's for a few minutes.

lucittm · lucittm's Garage

Our cars have a "safety feature" that prevents the fuel pumps from running if the airbag deploys. This is accomplished by removing the +12V from pin 7 (terminal 86) of the fuel pump relay coil. You can test this by connecting a voltmeter from pin 7 of the relay receptacle to ground, you should get +12V when the key is in the on position, you are getting battery voltage, so that is good. If there was no voltage, I'd check connector pin 18 (black wire with a white stripe) coming from the Airbag Control Unit behind the instrument panel.

The other side of the relay coil gets its ground from the Turbocharger Control Unit (P/N 965-618-130-00) under the driver's seat. If you are not getting a solid ground on the #6 terminal of the 6-terminal plug under the driver's seat with the key in the on position, you may need a new control unit. The ground signal originates on the intercooler and goes through the overboost switch on its way to the control unit. I would check there first. But based on your description, you may have caused a surge that fried your turbo control unit since it is connected directly to the battery on connector pin 6 of the control unit. 40 amps is a lot of amperage. You should stick with a 10-12 amp charger.

Mark

964 T #304 · 09-14-2009, 07:01 PM

Mark, thanks for the reply. Sounds like everything cks. out with what you said, as I have 12.83 volts comming from the Air bag control unit with the key in on position. But the ground side comming from the turbo control unit only reads .85 volts if I ck it between the 12 volt power or the 12 volt air bag side to the turbo control unit to the ground side.Is the turbo control unit something that we have to have? It sounds expensive! Thanks for your time.

lucittm · lucittm's Garage

OK, the way our relays work, they need a difference of potential of about 10V to latch. You have +12.83V on one side and +0.85 volts on the other. That represents the .85V drop across the relay, not enough to energize the relay. What you want to do is check for a ground path at the relay socket.

Change your meter to resistance scale and measure the resistance from a chassis ground to terminal 85. The resistance should be very low, maybe 10 ohms or less. If it is high, then you have to find the break in the circuit from the fuel pump relay terminal 85 to the ground in the intercooler. If you cannot locate a break, it is likely your control unit.

The unit is necessary to switch the fuel pumps on and off in overboost situations and route the ground signal correctly when the key is on.

Mark

964 T #304 · 09-16-2009, 08:38 AM

I wonder if it would possiable to route around theTCU as I do not and do not plan to use the over boost switch as I have had it grounded for a number of years an run the car on 1 bar boost. I still have a hard time beleiving this could be the fault of hooking the charger up on 40 amps, as the car has fuses on everything possiable for protection, and they are all still good. I wish I new more about the Imobilazition part of the alarm system. The TBC also looking @ wireing dia. supplys a signal to the EZ69 control unit when the key is on , and I have Nology plug wires and installed a firing tester on #3 cylinder and have killer spark spinning over with the key. AL

JFairman · 09-16-2009, 10:01 AM

When I was having frequent intermittant electrical problems with the simpler overboost circut in my 930 I considered ditching all that crap and manually wiring the fuel pumps and igniton to some high amperage toggle switches mounted under the seat nexto to the relays there or in the trunk for those times the key wouldn't do anything other than spin the starter motor...

Never did it though, at least not yet since resoldering all the solder points on the 2circut boards inside the yellow relay seems to have fixed that.

mark houghton · 09-16-2009, 11:33 AM

Quote:

Originally Posted by 964 T #304

....I do not and do not plan to use the over boost switch as I have had it grounded for a number of years an run the car on 1 bar boost.

Living on the edge, IMHO. It doesn't matter if you have your boost set at 1.0 or .8 or whatever. All you need is to have your wastegate fail you just once and boost spike up beyond what the motor can handle, and the damage is done. I look at it as cheap insurance.

A930Rocket · 09-16-2009, 01:02 PM

I grounded the fuel pump relays with an inertia switch years ago and haven't looked back. Did the Lee Rice wiring upgrade at the same time.

Never been happier.

Quote:

Originally Posted by JFairman

When I was having frequent intermittant electrical problems with the simpler overboost circut in my 930 I considered ditching all that crap and manually wiring the fuel pumps and igniton to some high amperage toggle switches mounted under the seat nexto to the relays there or in the trunk for those times the key wouldn't do anything other than spin the starter motor...

Never did it though, at least not yet since resoldering all the solder points on the 2circut boards inside the yellow relay seems to have fixed that.

964 T #304 · 09-16-2009, 03:16 PM

Mr930 rocket could you explaine the grounding with an inertia switch.

mark houghton · 09-16-2009, 07:08 PM

Quote:

Originally Posted by 964 T #304

Mr930 rocket could you explaine the grounding with an inertia switch.

Alll those funky relay and sensor circuits keep the fuel pumps from running unless the engine is pulling air across the metering plate. Thus, they won't run unless you're cranking the engine and drawing in air. Supposed to be a safety feature to stop the pumps from running in the event of a crash where the eingine is no longer running but the ignition key is still on. The inertia switch he's installed will cut the juice to the pumps when jarred in a collision.

964 T #304 · 09-17-2009, 03:50 AM

Thanks ,Mark for the explanatinon. Kindia like the air bag type shock sensors used in some cars. The overboost sensor can fail as well as the wastegate as it is just a hobbs switch which I have had fail on racing nitrous out board engines before. I will probably install an adj. hobbs switch now with the new turbo as it is capable of creating an overboost situation. Thanks

964 T #304 · 09-18-2009, 09:06 AM

Well I found a used one @ DC automotive and ordered it as they replyed to an add I posted in the want adds on our host site and had it shipped next day red label am delivery. They called me back yesterday afternoon to confirm correct part # and again ask me if I wanted an A.M. delivery or an afternoon delivery and I told them that I needed an A.M. delivery. I sat around this morning waiting on it and it never came so I called to get a tracking # and was told that it looked like that I was charged for next day air but it was shipped regular ground, so now it won't come for three to four working days. " DC Automotive You suck"

JFairman · 09-18-2009, 09:41 AM

I got a new overboost sensor from pelican because mine would shut the pumps down at about .95 bar sometimes.
It was a special order item they don't keep in stock and it was called charge pressure sensor or something like that. It's about $60 new.

When new they don't break the ground till about 1.3bar supposedly. Havn't tried it to find out.

lucittm · lucittm's Garage

Don't forget that the safety circuitry also shuts down the fuel pumps in the event of an engine fire when the engine stalls. Bypassing this circuitry and installing an inertial switch will allow the fuel pumps to continue to pump fuel at high pressure into the rubber lines in the engine compartment if you have a fire that was not caused by an impact.

One more note, the overboost switch removes the ground from the fuel pumps and is very quick to reduce an overboost situation and then reset to allow normal operation of the fuel pumps. If you unscrew the sensor switch you will see that it senses through a small orifice. This prevents short boost spikes from lifting the ground. Removing the overboost switch completely will allow momentary boost spikes to affect the engine. I know this because I (unknowingly) had a 1.0 bar spring installed in my waste gate and I bypassed the boost switch. The result was broken piston rings in cylinders 4, 5, and 6.

If your overboost switch is activating, find out why and correct the situation or install a new switch that allows slightly higher overboost such as 1.5-1.8 bar. Anything over 2.0 bar in a stock engine, even momentarily, has been reported on this board as destructive.

Thanks,
Mark