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Question Fuel Pumps NOW running when key is On...

Guys,

It's been a while since I posted on the forum - - been enjoying driving the car...

I noticed yesterday that the FP's are now running when I turn the key ON. I checked the Air Flow Meter Switch and it's securely in it's correct place - even plugged/unplugged a few times. Is there a way to check this switch or plug? Is the switch always OPEN when car is Off and Closed when car running? or, opposite?

Both of the FP Relays are pulling in at Key On.

Can anyone help me diagnose this - - thanks! Shannon

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LIVN80S - - Red '79 Porsche 930 Steel Slant Nose Conversion [in 1987] w. 46k miles 3.3L; 964 Cams; K27HF @ 1.0 BAR, with Garrettson Intercooler; Rarly Zork; CIS Flowtech Fuel Head & BL-WUR.

Last edited by mooney265; 03-18-2018 at 05:54 AM..
Old 03-18-2018, 05:36 AM
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It could be the relay in the engine compartment. One failure mode is an open circuit which will allow the pumps to run when the key is on. Quick test is to pull the relay and see if the pumps run with the key on but engine off.
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Old 03-18-2018, 06:13 AM
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Yellow relay caused that exact issue for me. I pulled it apart, soldered the broken joints and put it back together. That fixed it for me.
Old 03-18-2018, 06:31 AM
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Ok, I have an '79, so no yellow relay... I do have another Red Relay at the engine compartment which matches the 2x Red ones at the Fuse Panel.

When I pull the Red Engine Bay relay, the FP's stop running. I had a replacement relay and replaced the engine bay one, but have the same results...

So, I'm still at: Turn key on and both FP Relays energize and FP's turn on...
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Old 03-18-2018, 07:11 AM
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Is there any over boost protection on your 79? Something has to be telling your relays when to energize, no? How did that system work before the yellow relay was introduced?

Edit, just re-read your post. So the red relay in the engine bay was replaced by the yellow one in later years? Maybe it's just poor connections if it isn't a bad relay?

Last edited by Jeff NJ; 03-18-2018 at 07:43 AM..
Old 03-18-2018, 07:38 AM
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You could have two bad relays. May want to check the relay by swapping with a red relay from the front trunk.

Rahl
Old 03-18-2018, 08:27 AM
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Quote:
Originally Posted by 356911930 View Post
You could have two bad relays. May want to check the relay by swapping with a red relay from the front trunk.

Rahl
I have 2x new relays and have switched the current ones out with these; still same issue...
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Old 03-18-2018, 08:37 AM
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Quote:
Originally Posted by Jeff NJ View Post
Is there any over boost protection on your 79? Something has to be telling your relays when to energize, no? How did that system work before the yellow relay was introduced?

Edit, just re-read your post. So the red relay in the engine bay was replaced by the yellow one in later years? Maybe it's just poor connections if it isn't a bad relay?
For this purpose I have 3 relays: 2 at Fuse Box and 1 at engine bay. They are all Red or Black Model: 911-615-108-01

I've changed out all of them and still have the same issue.
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Old 03-18-2018, 08:39 AM
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For the past 9+ years of ownership, the only way I could get the car to mimic this would have been to "Unplug the Air Plate Switch" located on the backside of the CIS intake [the Blue Connector]. Like I stated on the original post, I've removed/replaced this multiple times today, but the pumps continue to run. The only way I've got the pumps to stop was by removing the Engine Bay Relay [RED].

I do have an overboost switch, and it works [at least it used to]. I'll check to see if I can get that to turn the pumps off, too [like it used to]. EDIT: Just tested the Overboost Switch - - works perfectly - - as in: I removed the connector with the ignition turned on [and pumps unfortunately running] and the pumps immediately stopped.

Shannon
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Last edited by mooney265; 03-18-2018 at 08:45 AM..
Old 03-18-2018, 08:42 AM
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A grounding issue anywhere in the circuit from the air meter switch to the red relay will leave the loop open which allows the pumps to run when the ignition switch is on. This includes the switch itself or the pick up points that open when the plate moves off its resting location. Have you cleaned the plug contacts in the air meter plate plug and receptacle?
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Old 03-18-2018, 09:08 AM
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Quote:
Originally Posted by RarlyL8 View Post
A grounding issue anywhere in the circuit from the air meter switch to the red relay will leave the loop open which allows the pumps to run when the ignition switch is on. This includes the switch itself or the pick up points that open when the plate moves off its resting location. Have you cleaned the plug contacts in the air meter plate plug and receptacle?
Thanks, All i've done [in past 30-min] is remove the air meter plate plug and "jumper it." It didn't have any effect and may not have. I just figured it's an "always open" circuit, and only closes when the engine is running - - was I wrong to do this?

Either way, when I jumped the plug, it didn't make a difference and the pumps continued to run... Shannon
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Old 03-18-2018, 09:15 AM
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If the pins on the plug are jumped it should close the circuit and cut the pumps. You'll need to trace connectivity of the wires to find where the break is.
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Old 03-18-2018, 02:49 PM
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Quote:
Originally Posted by RarlyL8 View Post
If the pins on the plug are jumped it should close the circuit and cut the pumps. You'll need to trace connectivity of the wires to find where the break is.
OK, that's what I'll need to do, then...

Anyone know where this circuit goes? Does it stay in the engine compartment, or come up to the front, or both? Thanks, Shannon
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Old 03-18-2018, 03:25 PM
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Here is the schematic for your pumps.
The earth to the o/boost sw has to be made for them to run.
If you disconnect it, do they still run? They shouldn't because the earth is for the power feed thru the engine bay relay. (G in schematic)
Do they still run if you pull the engine bay relay? They shouldn't - and if they do, that means the front relays are getting their earth from somewhere else (a short).
Your airplate sw (F) provides an earth circuit to energise your G relay, which in turn provides the circuit to energise the front pump relays - thru the o/boost sw.
I can't at the moment figure how the airplate sw is operating - when you pull the plug the pumps run - but the plug wires go to either side of the sw in the schematic - hopefully someone can fill that gap.
but somewhere it looks like you have an errant earth (short) in the energising circuit. I think the airplate sw is adjustable? Guys?
If you pull enough of these circuit bits - o/boost sw, airplate sw, rear relay we should be able to tell which bit of circuit you need to look at. If none of these have any effect, the earth is in the front relay circuit - because the o/boost sw, airplate sw, rear relay all work on the circuit to energise the front relays.
Alan
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Old 03-18-2018, 03:51 PM
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Alan,

Thanks for the schematic... I'll study real close tonight...

Here's what I can report:
1. All electrical bits in their place and turn on key and Both Pumps Run [used to not]
2a. Remove Air Flow Meter Plug - both pumps continue to run.
2b. Jumper Air Flow Meter Plug with Paperclip - both pumps continue to run.
2c. Keep Air Flow Meter Jumpered with Paperclip...
2d. Go to engine bay and remove overboost switch - pumps stop.
3. Replace OB Switch - pumps run
4. Remove Single Relay for OB Switch - pumps stop.
5. Replace Single Relay - pumps run
6. Remove Front FP Relay - One pump stops and other continues.
7. Replace FP Relay - Both Run
8. Remove Rear FP Relay - One pump stops and other continues.

This is where I'm at... I'll look at the diagram and report back. Thanks! Shannon
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Old 03-18-2018, 04:10 PM
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cis-'air flow plug'

On Post #7 of this thread, Mark H. has attempted to explain the system. I'll have to make sense of it, as I'm still confused as to why the pumps don't stop when I jumper this plug. Maybe I can run ohms from each of the plug's leads to ground and see if there is a direct contact to ground?

Shannon
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Old 03-18-2018, 04:21 PM
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Quote:
Originally Posted by mooney265 View Post
cis-'air flow plug'

On Post #7 of this thread, Mark H. has attempted to explain the system. I'll have to make sense of it, as I'm still confused as to why the pumps don't stop when I jumper this plug. Maybe I can run ohms from each of the plug's leads to ground and see if there is a direct contact to ground?

Shannon
There should be a ground on one side of the air plate PLUG, and not the other. If you can, get you ohmeter across the sw terminals when plug removed. Move airplate slighty - I know - running out of hands. But drop a weight on it so it is open (not something that will fall down hole - screw driver handle or similar. Then close plate and measure again - same or different. I am suspicious that it is adjustable, and may be out of adjustment. Been a while since in there.
Alan
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Old 03-18-2018, 04:27 PM
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Quote:
Originally Posted by Alan L View Post
There should be a ground on one side of the air plate PLUG, and not the other. If you can, get you ohmeter across the sw terminals when plug removed. Move airplate slighty - I know - running out of hands. But drop a weight on it so it is open (not something that will fall down hole - screw driver handle or similar. Then close plate and measure again - same or different. I am suspicious that it is adjustable, and may be out of adjustment. Been a while since in there.
Alan
For right now, I can say for certain there is a ground on just 1-side of the AF Plate PLUG... However, both sides of the PLUG have Ohms to one of the Rear Relay Socket Plugs. Not too sure what that means...

I'll have to do the 3-handed dance tomorrow, as I'm not going back out to the garage again tonight [said that 3x already]... But really, that's it on the garage for tonight

Shannon
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Old 03-18-2018, 04:40 PM
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Quote:
Originally Posted by Alan L View Post
There should be a ground on one side of the air plate PLUG, and not the other. If you can, get you ohmeter across the sw terminals when plug removed. Move airplate slighty - I know - running out of hands. But drop a weight on it so it is open (not something that will fall down hole - screw driver handle or similar. Then close plate and measure again - same or different. I am suspicious that it is adjustable, and may be out of adjustment. Been a while since in there.
Alan
Hey Alan,

I don't think the air plate switch itself is adjustable. Only the metering arm/plate is adjustable, which I would advise against in this scenario.

Bad switch (it's normally closed, opens when the metering arm is deflected), or the ground wire that corresponds to the "one side of the air plate plug" that you refer to. If I read all the schematics correctly before leaving my post way back in 2010, we need to interrupt the ground for the pumps to run (on an '87 anyway). That's accomplished by pulling the plug, a bad switch that no longer closes at rest, or a wire fault back to the relay. I think....anyway.

If it's the switch, it would appear to be a pain in the royal ass to get to for replacement. Even testing said switch with an ohm meter is a PITA.

Shannon, stay with it or ignore it...other than the accident safety reason for this whole weird electrical crap that the good Dr. Porsche dreamed up.
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Old 03-18-2018, 06:26 PM
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Yes, I am thinking switch. Sorry, bit brain dead right now to figure that part of schematic - what Mark says about breaking ground makes sense in a practical way. But I cannot relate it to the schematic. It is telling me something different.
One thing you could do, is pull pumps front relays (so they don't operate), turn key on and just open/shut airplate. If the sw is working you should hear click/click as the rear relay operates in concert with the sw.
At least with your problem, you have pumps. Most of the problems posted don't have pumps working :-)
Alan

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