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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: 2Bad360sfromNC]
#1660358
09/06/14 06:49 PM
09/06/14 06:49 PM
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Joined: Jan 2003
Posts: 28,114
Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,114
Irving, TX
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That's why I posted that pic on page 1.  Wastegates get some people a bit mixed up.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: feets]
#1660359
09/08/14 07:59 PM
09/08/14 07:59 PM
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Joined: Feb 2003
Posts: 4,837
Castlegar, BC, Canada
That AMC Guy
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Castlegar, BC, Canada
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Allrighty! Latest News.
New fuel filter went in. Could still blow through old one, gas was nice and clean.
Put fuel pressure gauge back on rail, took car for a rip. Couldn't get more than 60psi on the fuel gauge when trying to boost, and also noticed that the bucking was occurring in relation to a drop in fuel pressure on the gauge.
Returned home, and tried to "deadhead" the pump by pinching off the return line. After pinching the line for 3-4 seconds, pressure started to climb steadily, but not by any means quickly. It reached about 70psi and called it quits. (And no, I didn't hold it there too long) and releasing the return line instantly returned the gauge to around 49-50psi at idle.
Weak pump?
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: gdonovan]
#1660361
09/08/14 09:57 PM
09/08/14 09:57 PM
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Joined: Feb 2003
Posts: 4,837
Castlegar, BC, Canada
That AMC Guy
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Castlegar, BC, Canada
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By the factory dash gauge, less than 5. More around the 2.5 - 3 psi range.... just tickling the turbo. I tried pushing the throttle for more boost and fuel pressure would not rise accordingly and was accompanied by more lurching.
A feller on the Turbo Dodge board gave me a bit of a formula for figuring out what pressure I need for boost over static pressure.
I need at least:
60 psi for 5psi Boost (which I'm barely getting)
66 psi for 10psi boost
71 psi for 15psi boost
He also said when I pinch off the return line I should also instantly see between 80 to 100 psi which I'm also not getting.
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: zrxkawboy]
#1660363
09/09/14 02:25 AM
09/09/14 02:25 AM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
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Posts: 27,421
Balt. Md
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From what I remember that system that had about 55 psi with the eng running and the vacum line hookede to the fuel press regulator. Pull the vacum line on the regulator and it would jump about 10 psi to about 65 and pinch the regulator return line line and instantly it would jump to about 100 and I mean right away. Seems to me even the non turbo systems like the V/6 mini vans that ran a system of about 38 to 48 psi would jump right to about 80 or more as soon as the return line was pinched. Thats about what I remember but its been years as Mopar went to the returnless EFI systems in the 90's on many systems. But if the press does not jump as soon as you pinch off the return line it sounds like the pump is weak. Is it weak enough to be your problem ?? Thats the question and as I said I have not worked on them for many years but it is more important for the reserve fuel pressure on the turbo cars. Ron
Last edited by 383man; 09/09/14 02:26 AM.
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: gdonovan]
#1660365
09/09/14 01:44 PM
09/09/14 01:44 PM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
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Joined: Jan 2003
Posts: 27,421
Balt. Md
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Quote:
Quote:
A feller on the Turbo Dodge board gave me a bit of a formula for figuring out what pressure I need for boost over static pressure.
I need at least:
60 psi for 5psi Boost (which I'm barely getting)
66 psi for 10psi boost
71 psi for 15psi boost
Nope its a 1:1 ratio.
0 boost = 55 psi
5 boost = 60 psi
10 boost = 65 psi
On the fuel pump- Early pumps would blow past 100 psi, later pumps and aftermarket top out at 70-85 psi.
You are having a low boost issue and the fuel pressure is fine, I think you are chasing a red herring at this point and you should focus on other areas.
A pound or two of fuel pressure will make no difference, these cars are not that sensitive to it.
I'd start with the basics- check your cam and distributor timing and go from there.
I would agree a few pounds off on the fuel press does not sound like your problem. Just curious if you could wire the wastegate open and drive the car on just the eng to see how it runs. I did that years back to see how the car ran without any boost and to see if the problem was still there. Ron
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: 383man]
#1660366
09/09/14 05:16 PM
09/09/14 05:16 PM
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Joined: Feb 2003
Posts: 4,837
Castlegar, BC, Canada
That AMC Guy
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Castlegar, BC, Canada
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The car runs perfectly fine as long as I don't get on the turbo. Only when I start boosting does the issue show up. Cam and ignition timing has not changed. Has never been touched. Quite literally, this problem appeared overnight. Saturday the car drove fine, didn't touch it Sunday, and then Monday it was being difficult. I've been following the how-to's on this webpage: http://www.turbododge.com/forums/f4/f14/358339-checking-fuel-pressure-84-93-turbo.htmlThis is the part that worries me about the output of my fuel pump: D)"Deadhead the Pump" by momentarily pinching off the return line, this will show you the pumps maximum output. Maximum output needs to be a minimum of 80 PSI and pressure needs to rise to max instantly. When I dead-headed the fuel, it took several seconds for it to even climb to 70psi and that was as high as it would get. It was most definitely NOT instantaneous.
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: gdonovan]
#1660368
09/09/14 10:23 PM
09/09/14 10:23 PM
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Joined: Feb 2003
Posts: 4,837
Castlegar, BC, Canada
That AMC Guy
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Well, I'll double check them, but I'm nearing the end of my rope with this car. Nothing seems to help it.
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: That AMC Guy]
#1660369
09/11/14 08:50 PM
09/11/14 08:50 PM
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Joined: Feb 2003
Posts: 4,837
Castlegar, BC, Canada
That AMC Guy
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UPDATE!
Back to basics. I do believe I found the smoking gun.
Dry Compression Test:
#1- 90 psi
#2- 130 psi
#3- 130 psi
#4- 130 psi
Plug #1 also has some silver speckling on the ground electrode. Methinks something may be askew in cylinder #1. Going to try a wet test to see what happens.
Wet Results:
#1- 100 psi
#2- 145 psi
#3- 135 psi
#4- 130 psi
Sounds like I've got a bad hole. The problem under boost must be a serious misfire.
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: That AMC Guy]
#1660370
09/11/14 10:07 PM
09/11/14 10:07 PM
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Joined: Feb 2003
Posts: 4,837
Castlegar, BC, Canada
That AMC Guy
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Now for the really stupid part. I changed to a fresh set of Champion plugs (the RN12YC copper cores) and the car runs fine again!!!  That low compression in #1 still worries me, but it's not lurching under boost anymore!! I can't believe that. I never would've guessed it was a bad/fouled plug. Thank you GDonovan for giving my head a shake. Back to basics for sure. I feel like such a jackass right now. I'll probably just drive the wheels off the ol gal until that #1 hole becomes a real problem then giver the full-meal-deal rebuild. She's too nice of a car to just throw away. Thanks for letting me pick your guys brains in for three pages! That's why I love moparts and have been an annoyance here for over a decade!! 
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting
[Re: Challenger 1]
#1660376
09/12/14 10:18 AM
09/12/14 10:18 AM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
How's the spark plugs and wires,cap etc? They need to be in top shape for boost.
Spark plugs are always the first thing I change on a boosted motor when problem occurs like yours. When you said the were 10 months new I was thinking that's not fresh for a boosted motor.
The spark plugs in my alky dragster with 60 lbs of boost only last for 1 run for about 5 seconds under power.
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