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-   -   What does it mean Basil? (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/458584-what-does-mean-basil.html)

Dave 86 930 Fl 02-21-2009 11:32 AM

What does it mean Basil?
 
Guys,

What does it mean when I remove the relay for "fuel pump II" (towards rear of car) while the car is running and the engine idles just fine, BUT, when I replace the FP II relay and remove FP I (towards front of car) the engine quits.

This is not a test, but a real life situation.

Regards, Dave

Dave 86 930 Fl 02-23-2009 03:34 AM

I thought I offered up some good clues for all of the "problem solvers" out there ... no takers?

930gt-40r 02-23-2009 05:20 AM

Maybe fuel pump 2 is dead, or maybe the car cuts out because fuel pump one needs to scavange the gas from the tank in order to make the car run and throws enough volume by itself to idle the car.

jwasbury 02-23-2009 05:21 AM

I think it means that the relay for FP II gets its power from the FP I relay. So pulling the FP I relay kills both fuel pumps and the car stops. The car will idle and run with only FP I working, so that's why it doesn't stop when you pull the relay for FP II.

930gt-40r 02-23-2009 05:33 AM

Is that true? That sux! However I think that the factory used the rational that if number 1 isnt working, number 2 wont have fuel and therfor burn up.
But I swear the last time I wired efi into someones car, the "turn-on" source was spliced together for both relays- which I used to turn them on from the computer.

sand_man 02-23-2009 05:34 AM

In case you get bored and need another project:
http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/424622-930-fuel-pump-relay-wiring-once-all.html

Dave 86 930 Fl 02-23-2009 08:42 AM

Quote:

Originally Posted by 930gt-40r (Post 4502274)
Maybe fuel pump 2 is dead, or maybe the car cuts out because fuel pump one needs to scavange the gas from the tank in order to make the car run and throws enough volume by itself to idle the car.

That's what I was thinking.

Dave 86 930 Fl 02-23-2009 08:43 AM

Quote:

Originally Posted by jwasbury (Post 4502276)
I think it means that the relay for FP II gets its power from the FP I relay. So pulling the FP I relay kills both fuel pumps and the car stops. The car will idle and run with only FP I working, so that's why it doesn't stop when you pull the relay for FP II.


That's an interesting thought, although I hope the folks at Porsche did better than that. I'll check that premise when I get home this evening.

Dave 86 930 Fl 02-23-2009 08:50 AM

another peice of information
 
I'll provide another bit of information ... The car is running lean at idle (15-16 afr) and rich (10 afr) at cruise. Under boost conditions the car stumbles and goes way lean.

I have spark. I'm fairly confident that there are no intake leaks. All fuses, relays and boost relays are operating properly. I have no idea what the system fuel pressure is, but the gauges are on the way from Pelican.

If you have any other questions, please fire away.

This reminds me of an episode of House. Let the games begin.

ClickClickBoom 02-23-2009 09:05 AM

Hello,
Without talking to Dr Porsche, I will bet that the design philosophy is similar to many other 2 pump designs. The first pump is a delivery pump, high volume, low pressure. The second pump is a pressure delivery pump, high pressure, low volume. The reason you are experiencing the symptoms of quitting when you pull the relays is because the rear pump is not working at spec and unplugging the front kills the supply. The lean running on boost points at reduced high pressure fuel and the resulting lean condition. I would suggest plumbing pressure guages after each pump and check outputs against the FSM for your car.
Hola
eric

equality72521 02-23-2009 09:41 AM

The power for the fuel pumps are parallel. Here is the schematic for a 1978 but it should be pretty much the same. Sounds like you have a bad pump or bad wiring. Time to break out the meter. "J" is fuel pump relay and "G" is fuel pump below.

http://forums.pelicanparts.com/uploa...1235410829.jpg

equality72521 02-23-2009 09:47 AM

Quote:

Originally Posted by ClickClickBoom (Post 4502594)
Hello,
Without talking to Dr Porsche, I will bet that the design philosophy is similar to many other 2 pump designs. The first pumpis a delivery pump, high volume, low pressure. The second pump is a pressure delivery pump, high pressure, low volume. The reason you are experiencing the symptoms of quitting when you pull the relays is because the rear pump is not working at spec and unplugging the front kills the supply. The lean running on boost points at reduced high pressure fuel and the resulting lean condition. I would suggest plumbing pressure guages after each pump and check outputs against the FSM for your car.
Hola
eric

Yes.

equality72521 02-23-2009 09:58 AM

I would start with the relay. Try replacing it with the horn relay just long enough to test and see what happens.

Dave 86 930 Fl 02-23-2009 04:05 PM

Quote:

Originally Posted by ClickClickBoom (Post 4502594)
Hello,
Without talking to Dr Porsche, I will bet that the design philosophy is similar to many other 2 pump designs. The first pump is a delivery pump, high volume, low pressure. The second pump is a pressure delivery pump, high pressure, low volume. The reason you are experiencing the symptoms of quitting when you pull the relays is because the rear pump is not working at spec and unplugging the front kills the supply. The lean running on boost points at reduced high pressure fuel and the resulting lean condition. I would suggest plumbing pressure guages after each pump and check outputs against the FSM for your car.
Hola
eric

The Porsche manual describes the process to check both pumps. I ordered a CIS tester today which will allow me to connect up to the rear pump and identify the bad pump, if there is one. I'm not convinced that I have a bad fp, as these cars are a bit tricky to diagnose and as a result, I'm reluctant to raise the victory flag just yet.

OSI930 02-23-2009 08:59 PM

I believe the front fuel pump has a check valve and the rear fuel pump does not. When you kill the front pump, the rear pump does not see fuel. The car will idle with the front pump only as the front pump will push fuel through the rear pump but the fuel pressure will be way off to run very well past idle.

Dave 86 930 Fl 02-24-2009 01:35 PM

Differential Diagnosis
 
Guys,

A little more information. I measured voltage and amperage for both fuel pumps. The manual states voltage should be ~ 11.5 and amperage should be in the range of 5-8 amps. I measure the voltage at the pump, whereas I measured the amperage at the relay. Here are the results:

Front FP: 11.1 volts & 7 amps

Rear FP: 10.6 volts & 6 amps

Because I suspect the rear pump has issues, I could look at the results and say they're a bit low. I ordered some special fittings today from Porsche ($50) that will allow me to test the fuel pressure with the CIS tester, so we'll see where that leads me. I should have the parts Friday or Monday, as they are being shipped from our friends in Germany.

If you have any other thoughts or comments, please feel free.

Regards, Dave

Dave 86 930 Fl 03-02-2009 04:47 PM

Running Like a Scaulded Dog
 
Guys,

I finally got the old 930 running again this weekend. I purchased the CIS gauge kit and the Porsche fittings for the fuel pumps, so I could check the various fuels pressures necessary for a healthy 930. First step, check the fuel pressure at the rear pump as per the Porsche manual, but there were complications. After disconnecting the plug at the back of the metering plate and turning the ignition key on, the front fuel pump was not running. Interesting Ö so I switched the fuel pump relays and now the back fuel pump was not running. I thought I had two good relays (checked and rechecked), but obviously I was wrong. So, armed with two new relays I measured the fuel pump pressure and it was a solid 4 bar, which was within the acceptable range of 2-4 bar. I had my money on a bad rear fuel pump, but this car has fooled me many times before.

I did take the red cap off of the bad (intermittent) relay and one of the contact wires looked like it has been cooked. I touched the wire with my fingernail and it moved away from the terminal Ö Now my confidence is rising, but I cautiously move forward with the rest of the tests.

I disconnected the fuel gauge from the pump and connected up between the fuel distributor and the wur Ö A brand new Brian Leask adjustable wur. Started the car for the first time in 14 months and watched the fuel gauge as the wur transitioned through its warm-up cycle, which precisely matched the specifications for my vehicle. I did have to make some adjustments to the AFR, which was accomplished with the Innovate wide band sensor. The Leask wur also has the rpm switch and I started with the 4000 rpm pill, which I can tune to put off the fuel enrichment cycle required for boost conditions.

Iíve only driven the car about 30 miles since itís been running, but it has never run as smooth as it is right now. The wur is working great, but I need to run some log files and take a look at some fine tuning. Iím currently running about 14.4 AFR at idle and cruise Ö Whereas; on boost Iím seeing around 11.9 with the 4000 rpm pill. Once I start getting some log files, Iíll try changing the pill to 4200 rpms and see how that works.

Kudos to Brian Leask, as the entire package that he provided (adjustable wur, rpm switch & manuals) was absolutely perfect. How about lessons learned, one for sure is I will be replacing my fuel pump relays and fuse every year whether I need it or not. These cars are a real trip, one that I enjoy the challenge of diagnosing, just maybe not so often.

If anyone has any questions, please ask.

Regards, Dave

BReyes 03-06-2009 10:16 AM

Great thread.

Now. Where is the info on creating a harness/relays/ 2pumps and all from scratch.

Build sheet needs work to finish fuel system design for TT project. Wait I am now into fuel cell discussion and I saw a surge tank at Billet Design that caught my eye, and I haven't began to think about.

PP can make Electrical Engineers. I mean there is no room for more college courses, and this stuff is a must. So where else are you going to get it than from the Pelican. BTw you guys are making UTi's what 51 week course look like a quick course. It takes years of questions.

Regards,

Chuck Jones 03-07-2009 05:40 PM

I've been running the LM-1 in the cabin, and found that I can wedge the LM-1 under the passenger side door handle....the spacing is just right for the LM-1 box to slide under the handle so that I can look over and see the AFR readouts as I drive. Before that, I had it on the seat where it would slide around and I had to grab it to see it. Not as professional looking as an AFR dial that fits in the clock cutout....but it works great...and is easy to see.

Dave 86 930 Fl 03-08-2009 05:35 AM

AFR Gauge Location
 
Quote:

Originally Posted by Chuck Jones (Post 4529387)
I've been running the LM-1 in the cabin, and found that I can wedge the LM-1 under the passenger side door handle....the spacing is just right for the LM-1 box to slide under the handle so that I can look over and see the AFR readouts as I drive. Before that, I had it on the seat where it would slide around and I had to grab it to see it. Not as professional looking as an AFR dial that fits in the clock cutout....but it works great...and is easy to see.

Chuck,

I have the Innovate gauge in the cabin, but location has been an issue so I've come up with an approach that will place the gauge in a better location. I removed the radio and had a composite plate made that has a recess for the gauge. This weekend I'm rewiring the gauge and all should be in place and I will post some pictures. I also plan on making a new gauge template from a piece of carbon fiber veneer that will display the digital AFR, but will cover up the lights around the perimeter of the gauge. I found a guy that will cut the CF template with a laser. The composite plate will have enough space to allow a second display and I'm thinking about a gauge that would monitor pre/post intercooler temperatures.

Regards, Dave


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