85 928 Fudl pump/electrical question
05-08-2010, 09:51 PM
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85 928 Fudl pump/electrical question
I hadn't driven my 85 S for about a week and I needed to use a 40 amp battery starter to ge it going today. I've been using an Interstate mp91 and will soon be switching to the yellow top optima that I purchased thru 944cup's thread.
Anyways, I drove it for close to thirty miles to a store, came out, and it wouldn't start. Turnded over but no smell of fuel. I swapped the relay with the blower relay and tested the fuel pump fuse. Both guaranteed to work. Still won't start. AAA came out and tried jumping me with their 24V cables off of a roll truck. No Luck. So - I get this nice ride back to my house in a tow truck (Yea for having AAA). Tried to start it at home...no luck. Placed the 40 amp battery starter back on it...started right up!
Questions:
1) when does the fuel pump engage? I thought I would have smelled gas around the exhaust pipes when it wouldn't start.
2) Anyone know how much amperage this needs to draw? I would have thought the AAA 24v cables would have produced enough current to have engaged the pump.
The only conclusion I could draw was the battery was too low in charge. Others thoughts??
Anyways, I drove it for close to thirty miles to a store, came out, and it wouldn't start. Turnded over but no smell of fuel. I swapped the relay with the blower relay and tested the fuel pump fuse. Both guaranteed to work. Still won't start. AAA came out and tried jumping me with their 24V cables off of a roll truck. No Luck. So - I get this nice ride back to my house in a tow truck (Yea for having AAA). Tried to start it at home...no luck. Placed the 40 amp battery starter back on it...started right up!
Questions:
1) when does the fuel pump engage? I thought I would have smelled gas around the exhaust pipes when it wouldn't start.
2) Anyone know how much amperage this needs to draw? I would have thought the AAA 24v cables would have produced enough current to have engaged the pump.
The only conclusion I could draw was the battery was too low in charge. Others thoughts??
05-09-2010, 04:32 PM
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1. What's a FUDL pump?
2. If they really applied 24V to your electrical system, you're lucky they didn't blow the LH, EZK, and a bunch of other stuff. These cars run off 12 - 14 Volts.
3. AFAIK, the fuel pump runs for a second or so when you turn the ignition on, then starts running again when you start cranking the engine. Someone more familiar with LH internals should be able to give a more definite answer.
2. If they really applied 24V to your electrical system, you're lucky they didn't blow the LH, EZK, and a bunch of other stuff. These cars run off 12 - 14 Volts.
3. AFAIK, the fuel pump runs for a second or so when you turn the ignition on, then starts running again when you start cranking the engine. Someone more familiar with LH internals should be able to give a more definite answer.
05-09-2010, 05:20 PM
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Originally posted by SQLGuy:"you're lucky they didn't blow the LH, EZK, and a bunch of other stuff. These cars run off 12 - 14 Volts."
Really Lucky!
Really Lucky!
Last edited by soontobered84; 05-09-2010 at 05:22 PM. Reason: quote repair
05-09-2010, 07:07 PM
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FUDL - my incompetence for wanting to type "Fuel" 
SQLGUY - I thought so too. The engine would turn-over, just not start. Therefore, I thought surely a) I'd smell gas at the exhaust pipes like if its flooded and b) I had the tow driver hold his hand on the underside of the gas tank for vibration and to listen if he could hear the pump engaging when I cranked the engine. Nothing. But as soon as I put the "quick start" from the battery charger to it...engine started immediately.
SQLGUY - I thought so too. The engine would turn-over, just not start. Therefore, I thought surely a) I'd smell gas at the exhaust pipes like if its flooded and b) I had the tow driver hold his hand on the underside of the gas tank for vibration and to listen if he could hear the pump engaging when I cranked the engine. Nothing. But as soon as I put the "quick start" from the battery charger to it...engine started immediately.
05-09-2010, 07:14 PM
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I would not use the "quick start" on the battery charger. Voltage is almost certain to be too high, and it will not be pure D.C. voltage. Way, way too much chance of blowing one or both of the ECUs or other electronics.
It is safe to use properly-connected jumper cables to a good twelve-volt battery.
It is safe to use properly-connected jumper cables to a good twelve-volt battery.
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05-09-2010, 07:44 PM
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I think the 928 is one of those vehicles that, if voltage drops too low, at just theo wrong time during cranking, gets into a no-start state. Mine got into a pretty bad state after flooding about a week and a half ago, but after evening out the electolyte levels in the battery (some cells were overfilled, and some were a bit low) and giving it a really good overnight charging, it's been fine.
Were you jumping it from the battery or from the charging post up front?
FWIW, ignition power comes straight off the battery. If the battery were really low, I think you could see much lower voltage at the EZK relay than at the alternator, when jumping from the charging post.
Were you jumping it from the battery or from the charging post up front?
FWIW, ignition power comes straight off the battery. If the battery were really low, I think you could see much lower voltage at the EZK relay than at the alternator, when jumping from the charging post.
05-09-2010, 08:30 PM
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try adding a battery cable to the ground of the battery and a good chassis ground this will tell you if your ground strap is not making a good connection
05-09-2010, 10:29 PM
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SQLGUY - both times when I quick started it, I did it from the front and not at the battery. AAA tried it with a battery pack in teh front and then with their cables from the rear but to no avail.
Merlin - I'll try that if I can replicate the problem again. Guess I'll keep that ground cable in the car for awhile once I get it. Wouldn't a continuity check with an ohm meter tell me if my ground is in tact?
I pulled my interstate battery out of the car today and checked it on the meter both with and without load and the meter states the battery is fine. I'm just fearful of getting stuck again and needing to be towed. It might be my imagination but when I threw the quick start with the 40amps at it, the motor turned much faster when cranking...could be my mind searching for a probable answer.....
Merlin - I'll try that if I can replicate the problem again. Guess I'll keep that ground cable in the car for awhile once I get it. Wouldn't a continuity check with an ohm meter tell me if my ground is in tact?
I pulled my interstate battery out of the car today and checked it on the meter both with and without load and the meter states the battery is fine. I'm just fearful of getting stuck again and needing to be towed. It might be my imagination but when I threw the quick start with the 40amps at it, the motor turned much faster when cranking...could be my mind searching for a probable answer.....