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Crotchety Old Bastard
 
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Fuel System Issue Diagnosis and the value of gages

Something you never want to see while cruising down the road:



While traveling to a local PCA event I merged on to an on ramp and gave 'er some throttle and the car bucked then shuttered as it struggled to get into boost. I looked over at my Fuel Pressure Gage and saw the pressure falling like a rock. AFR was also falling in unison. Backed out of the throttle and took the next exit off the freeway. My first thought was I have lost power to the WUR. Part of the process of restoring this car was that I completely disassembled the fuse box, cleaned everything the reinstalled new fuses and new relays. The rear fuel pump had a new style fuse added. This made me confident that fusing and relays were not the problem. I have seen in other turbos instances where the engine wire harness looses continuity of the Red/White wire feeding the CIS daisy chain from pin 10 on the 14 pin connector. I feared this is what had happened.
As I drove (more like idled in high gear) the backroads to home things got progressively worse. I noted that morning as I always do when starting the cold car that the Cold Control Pressure was 20psi. The control pressure was now dropping below 20psi and AFR was 9.4:1, yikes! Smoke began pouring out of the back of the car and no throttle was accepted. At that point the focus became really intense as I had a mountain to climb on the last leg of the trip home, and it appeared I had also lost a fuel pump or had a serious problem with the Fuel Distributor Pressure Regulator.
Got 'er home and shut it down. Fuel Pressure was 17psi and AFR 9.1:1.
Started checking electrical connections and the WUR was dead.
Pulled the 14 pin plug, checked continuity to the WUR and there was continuity.
Unplugged the fuel cutoff safety switch and hit the key, no rear fuel pump.
Moved up front to check continuity from the fuse panel to the rear pump via jumper wire from Relay #30 to #87, fuel pump fired up. Plugged in my spare (new) relay, hit the key and the fuel pump and CIS daisy chain lit up. SOAB! That new freaking relay had failed!



So I missed one of the most enjoyable PCA events due to a bad newish relay and I had a spare new one in the trunk. Several morals to this story:

> DO NOT BUY THOSE GOD FORSAKEN CHINESE PIECE OF $HIT RELAYS.
> Install gages in your cockpit, they will save you a LOT of troubleshooting. Had it not been for those 2 gages I would have thought I blew my engine or had something else seriously wrong with it. In this case you don't need both fuel pressure gage and AFR as AFR alone told the story. The fuel pressure gage just backed it up. I knew there was a fuel problem and the smoke blowing out behind me was fuel and not oil. BIG relief!

Also it was very educational to see real-time the symptoms of a dead relay. The AFRs went to 9 and fuel pressure went BELOW cold pressure range for the ambient temperature. Also good to know that the front pump can limp you along for a few miles. In my case it was 12 miles with half going up a mountain.

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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 02-05-2017, 08:22 AM
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Brian,

Congrats on a job well done. Proves your point! I love happy endings.

Rahl
Old 02-05-2017, 08:56 AM
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Unfortunately - and correct me if I'm wrong - all the fuel relays are now from "across the pond". Even those from our host, or so I've heard. Please tell me it's not true!

Can't say enough about information flow, i.e., gauges. They make us all senior diagnosticians. Glad you made it home. I hate being stranded.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 02-05-2017, 12:31 PM
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Another case for a good quality hidden high amperage Double Pole Single Throw toggle switch that bypasses all the relays and supplies the fuel pumps with 12 to 13.5 volts directly from the battery.

You can splice and solder the 12v supply wires from the DPST switch to the original thick red wires going from the back of fuel pump relay sockets in the front trunk down to the fuel pumps.
That's way easier than running new 12v supply wires all the way to both fuel pumps but if the original ones are sketchy then you have to.
Old 02-05-2017, 09:25 PM
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I had that same rear pump kill happen to me at The Ring (short burned some wires) with eye watering richness when limping. One might try adjusting the co-crew if the problem is spotted and no spare relay available. My fuel pumps are relayd separately on the console so I can test on the fly.


Its also a good time to drain the fuel tank and check the fuel tank strain/filter. Mine was so filthy and grimy I just ordered a new one. One of the reasons I chose to go EFI this year was the front pump having too much noise (also lean top end when high boost) and I should have checked the in tank filter sooner but as its a bit messy I tried a new front pump instead and it did not help with noise so I hope it was this clogged up filter to some extent. For some reason the tank itself is nice and clean inside?

Now I need to rethink if I will go straight to EFI or try my CIS once more to see how it works with the modded WG path (elephant delete) and tight exhaust flange with good flow from the tank.
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Last edited by smurfbus; 02-06-2017 at 04:41 AM..
Old 02-05-2017, 09:41 PM
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Brian,
Thank you for your good experience feedback!
Old 02-06-2017, 02:49 AM
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Bucketlist
 
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Thanks Brian, You are my main motovation for installing afr and volt gauges in the console and fuel pressure gauges in the console and in the engine compartment. These have saved me more than once and make CIS much easier to adjust.
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Old 02-06-2017, 05:17 AM
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At what point will out host finally stop selling this garbage?
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Old 02-06-2017, 10:46 AM
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Next mod on my list is updating fuse panel and switching to tyco box style relays
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Old 02-07-2017, 03:50 AM
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Crotchety Old Bastard
 
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Glad to pass along whatever tidbits I can to help keep a brutha' on the road!

Quote:
Next mod on my list is updating fuse panel and switching to tyco box style relays
That may be my next mod as well. My goal has always been to make this car the daily driver that the Red Rocket was. I thoroughly enjoyed that car. To think that a $30 relay is blocking that reality is so unacceptable.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 02-07-2017, 04:53 AM
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I've said it before and I'll say it again: don't waste money on electrical parts that do not come in a Porsche box.
Yes those parts are 2x + more expensive but they are reliable and function as intended by the factory.
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'91 964 3.3 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, H&R Coilovers, ESB spring plates- 210 lb
Old 02-07-2017, 06:11 AM
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Mighty Meatlocker Turbo
 
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I had a similar deal with a new relay recently, butt was the overboost relay and labeled Wittren/Made in Germany - lasted less then 300 miles before failing while cruising at 80mph on a very busy highway in Ft. Worth, Texass.

That is the only brand that Pelican sells - haven't looked at other sources yet to see what alternatives there are. Pelican took the relay back for store credit as I did not want them to send me a replacement (can only assume it will be junk, too).

Jims emergency mod above is on my list for sure!

Last edited by Rawknees'Turbo; 02-07-2017 at 09:41 AM..
Old 02-07-2017, 09:39 AM
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Crotchety Old Bastard
 
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Isn't that sad though that we even entertain the idea of hot wiring around a relay because all you can buy is junk!? Wow.
The relay that died on me was purchased here as a Porsche factory part. Paid 2x the cheap Chinese part price, then when I get it those loathsome words "made in China" are stamped right on it.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 02-07-2017, 10:35 AM
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this may be a good opportunity to ask about dash gauges.

for my 78 SC/930 conversion, I will be having Timmy2 make ALL NEW wiring harnesses. almost have tub stripped and about to pull the windshield so I can remove the dash.

so time to start planning the dash layout.

I plan to install a separate dash switch/relay for each pump and for the twin plug IGN.

the only two additional gauges I know I want is fuel pressure and voltage.

unless there is a compelling reason I plan to keep the stock fuel level, oil tank level, oil temp and oil pressure gauges.

and I will replace the 2.0 bar boost gauge with a AFR/Boost combo in place of the clock.

at this point have not done enough research to determine what else, may start a new thread depending on the reply and links to other discussions.

thanks.

suggestions?
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Old 02-08-2017, 08:45 AM
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Quote:
Originally Posted by RarlyL8 View Post
Isn't that sad though that we even entertain the idea of hot wiring around a relay because all you can buy is junk!? Wow.
The relay that died on me was purchased here as a Porsche factory part. Paid 2x the cheap Chinese part price, then when I get it those loathsome words "made in China" are stamped right on it.
Wow.
If Porsche is shipping junk as O.E. parts now, we are well and truly f***ed.
Will Pelican make it right?
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Paul B.
'91 964 3.3 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, H&R Coilovers, ESB spring plates- 210 lb
Old 02-08-2017, 09:54 AM
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Crotchety Old Bastard
 
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From what I understand Porsche now buys these relays from China. Same exact junk as branded other supplier at half the cost. Yes it appears we are screwed and need another option.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 02-08-2017, 11:13 AM
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Quote:
Originally Posted by RarlyL8 View Post
From what I understand Porsche now buys these relays from China. Same exact junk as branded other supplier at half the cost. Yes it appears we are screwed and need another option.
At half cost, buy a bucket full for spares. We'll probably need them. Every one in a hundred will probably hold together for the long run. Quality control is a foreign subject for the Chinese, they're all about selling quantity to fund their economy at our expense. Maybe der Trumpster can fix this.
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Old 02-08-2017, 05:54 PM
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Before I finished your first paragraph I guessed relay, but only because I had the exact same symptoms once.
In my case, the fuse box cover doesn't snap on properly anymore, and with gravity it and the little pieces of carpet on it had slipped down and tugged one of the relays partly out of the socket. It was probably the easiest "fix" in my ownership.
Last year I went with JohnyH blade fuse box but regrettably it doesn't address the round relays over the fuse panel. And my cover still doesn't snap on, lol.
I carry a box of relays, fuses, air injection exhaust plugs, diagrams to jump yellow relays, rabbits foot, you name it. All this hard won electrical knowledge- these cars suck electrically.
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Last edited by gsxrken; 02-08-2017 at 06:52 PM..
Old 02-08-2017, 06:47 PM
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Crotchety Old Bastard
 
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My first thought would have been relay or fuse had I not just changed out all of them for brand new. Once I did figure out it was the relay I was so disgusted with myself for missing the PCA event. I had a new relay in my tool kit and could have just popped it in and been back in business. God forbid there is a next time I will check the relay first. Yes I just bought 3 used German relays and will test them all and keep in my tool bag in the trunk.
These electrical issues are what keeps me from trusting the car to travel long distance which is really a shame. I'm slowly sorting my way through the car but there is still a lot of original wiring. I have a new found appreciation for the old Red Rocket. I took that car down to the empty tub during the repaint and checked every wire on it during reassembly. I trusted it completely and drove it on several long trips. It never let me down, I want to experience that again with this car.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 02-08-2017, 07:29 PM
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Mighty Meatlocker Turbo
 
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Quote:
Originally Posted by gsxrken View Post
. . . All this hard won electrical knowledge- these cars suck electrically.
And what is really bizzare about the suckage is that 944s/951s of the same years, do not suck. My brother has a 1986 951 and its electronic componentry is totally "modern" for its time (unlike my 1987 930, which is very 1950s-1960s) - blade fuses, standard style relays still used on today's cars, much better fusing practices, etc. That just doesn't make any sense.

Old 02-08-2017, 07:39 PM
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