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78 930 back up it was a fuel pump
Cheers to JPNovak here on the forum. My fall back when I struggle.
My 78 930 was hesitating when accelerating in 2nd, 3rd, (didn't try 4rth) when going into boost, but not in 1st. I could go to 6k on the tach in 1st no hesitation. I could "slowly roll" into full boost but it was like shifting a worn 915 (gently done with praying going on). It cruised along at a fixed speed fine. I could do 90mph (if I were to do that on a public road...) provided I moved toward that number carefully. I didn't have a way to load test the fuel flow. I have flow tested before several times on the same car when I had a similar problem(s) that revealed nuthing (that's right with a "u"). I asked a friend (JPNovak aka "Nanoman") his thoughts and he suggested a restrictive fuel filter might be the cause. I skeptically tried it (no offense Novak) and it didn't work. I still had the same problem. Nanoman then thought it might be the "other" fuel pump that was not replaced. To explain further; the new front pump and the weakening rear pump were adequate to drive on and even slowly go into boost, but as fuel demand/load increased the fuel pump could not keep up pressure thus causing the hesitation until I let up which would briefly allow the fp(s) to catch up. Armed with that theory I called Mike at Turbokraft (these guys are great) and ordered a Bosch Motorsport "044" fuel pump with the needed adaptor fitting for the rear (there are two different ones for front and rear). I just installed it, took the car out for a spin and went into boost once I got to proper operating temps. I romped on it a few times and before I knew it I was looking in my rear view mirror for "Johnny Law" as my car is far from quiet as some will attest to and clearly pulling away from traffic as if I had just stolen the car. I thought I would post this as I am sure with the summer heat there will be some fuel pumps giving up and/or weakening. There is one other thing going on that I think I know the cause. I keep "re-clocking" my speedo to the left and I keep loosing my needle to the right...  Next I can fix my fg tea tray that ripped off in flight while on the toll way!  *note. Stay tuned to JPNovak postings for CIS and MFI to EFI conversion hardware that is affordable for the regular guy!
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John- 78 Slick Top 930 "Illegitimi non carborundum" Last edited by sundevil64; 08-02-2013 at 05:37 PM.. |
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08-02-2013, 05:31 PM
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I would rather be driving
Join Date: Apr 2000
Location: Austin, TX
Posts: 9,108
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Woohoo! Boost away! glad to hear that you are in the Fast Lane again.
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Jamie - I can explain it to you. But I can not understand it for you. 71 911T SWT - Sun and Fun Mobile 72 911T project car. "Minne" - A tangy version of tangerine #projectminne classicautowerks.com - EFI conversion parts and suspension setups. IG Classicautowerks |
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08-02-2013, 06:16 PM
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Registered
Join Date: Nov 2001
Location: Austin, TX
Posts: 1,417
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Great John!
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08-02-2013, 06:20 PM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,125
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Good to hear John. Get the header fixed?
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08-02-2013, 07:51 PM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,125
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BTW, I have 2 -044's.
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08-02-2013, 07:52 PM
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Tippy,
Yes, the header is fixed. Jamie welded a patch on and I found another spot. As soon as I touched it with the tig it blew out with low amperage. All fixed and clear of slag. Fortunately, where I had to address an issue it was right where I could clean up any possible slag. I really didn't get much on the inside. The outside was another story. It's not like I tig much. I can melt metal that much I can say. I almost did that. It is my understanding the one 044 can nearly support a modified 930 motor? Where there any fitment problems in the front? It's a tight space. What did you do for an adapter fitting for the outlet at the tank? or did you modify that also? I read your email on the turbos you have been playing with. I will probably go with a ball bearing turbo in the future. I think the seals are starting to go on mine due to the oil drain mod I had to do to the sump. Keep me in the loop. I'm interested in seeing what you come out with.
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John- 78 Slick Top 930 "Illegitimi non carborundum" |
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08-02-2013, 08:52 PM
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Banned
Join Date: Nov 2001
Location: top of 3rd
Posts: 4,336
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John-
Curious on your symptom. I'm wrestling with a part throttle dead spot (flame out) that once I 'pedal thru' the car rockets off no problem. But load it up / bog 4th (under 2900) and soon as the boost begins to build it falls on its face hard (huge dead spot). If I feather the throttle thru 'that; tho, it zooms of fine. I was somewhat suspecting weak fuel delivery, as I swear I hear the rear pump whizzing away inside the car more than I'd used to. Was your symptom at all similar? |
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08-03-2013, 05:50 AM
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My fp wasn't making any strange noise this time, but it hat been at one point in the spring. It seem to be fine and I let it ride.
I didn't have a specific dead spot. It was only when I was giving it too much throttle that it would stumble. The tell tale was the ability to still get into boost with gradual throttle. You have jetronic on your 87 and I am not familiar with Jetronic and how it plays a part in the fuel delivery.
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John- 78 Slick Top 930 "Illegitimi non carborundum" |
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08-03-2013, 06:03 AM
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Quote:
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Jesper Carrera 3.0 1975 930 1978 OEM Matte Schwartz, ANDIAL IC, BL WUR, SC cams. LMA-3 w. XD-16 and CP transducer www.stauningwhisky.dk |
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08-03-2013, 08:10 AM
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