Replaced Gas lines in Engine Compartment, now it's not running right
11-13-2018 | 01:28 PM
#1
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Joined: Dec 2017
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From: Miami Florida
Replaced Gas lines in Engine Compartment, now it's not running right
I replaced the original circa 1986 rubber gas lines in the engine compartment of my 1987 924S with the Rennbay kit. (The car ran fine but there were bubbles in the rubber hoses.) It was a tight fit working behind the Power brake drum, but I was able to cut the original lines with the provided pipe cutter and bolt the new lines with the compression fittings using 3/8" socket extensions and a 17mm crows foot dropped behind the brake drum and a 17 mm next to the oil dipstick, which I took out to make room for the operation. This process took me working on a Monday, Wednesday and Friday about 2 hours per session or aprox. 6 hours. I'm a slow worker because I think too much, look too much and try and understand everything about German engineering and how the car works etc.
When the new lines were in place I started the car like the instructions said and shut it off to check for leaks.
There was no leaks, however a new problem. I wasn't able to get the RPMs above 4,000 without it cutting out. Then it dropped down until I feathered the throttle and got it back to above a thousand, then 2 then 3 and at 4 it konks out again. So I was theorizing a couple things that I did during the fuel line change that might have affected the performance. 1.) I did pinch the fuel line with a clamp in the back out of the tank to the fuel pump, after a week of being pinched I let it loose and it didn't immediately come back to original shape, so I thought maybe the hose is still constricted inside cutting off the fuel supply which is the cause of the engine cutting off when the RPMs go up... Makes sense, but I'm not sure. It's a cheap $20 hose so I plan on replacing it. 2.) My second theory is that something broke loose inside the rear tank to fuel pump hose (like old fuel sludge, the car sat in a garage for a year before I got it) and got into the fuel filter causing it to clog and that's the problem. 3.) My only other guess is that some vacuum hose is off or leaking and that's affecting the performance.
Any suggestions or ideas? I don't have a fuel pressure gauge YET, but I see I will need one to further troubleshoot this issue.
Thanks for any help.
When the new lines were in place I started the car like the instructions said and shut it off to check for leaks.
There was no leaks, however a new problem. I wasn't able to get the RPMs above 4,000 without it cutting out. Then it dropped down until I feathered the throttle and got it back to above a thousand, then 2 then 3 and at 4 it konks out again. So I was theorizing a couple things that I did during the fuel line change that might have affected the performance. 1.) I did pinch the fuel line with a clamp in the back out of the tank to the fuel pump, after a week of being pinched I let it loose and it didn't immediately come back to original shape, so I thought maybe the hose is still constricted inside cutting off the fuel supply which is the cause of the engine cutting off when the RPMs go up... Makes sense, but I'm not sure. It's a cheap $20 hose so I plan on replacing it. 2.) My second theory is that something broke loose inside the rear tank to fuel pump hose (like old fuel sludge, the car sat in a garage for a year before I got it) and got into the fuel filter causing it to clog and that's the problem. 3.) My only other guess is that some vacuum hose is off or leaking and that's affecting the performance.
Any suggestions or ideas? I don't have a fuel pressure gauge YET, but I see I will need one to further troubleshoot this issue.
Thanks for any help.
Last edited by 911Ragtop; 11-13-2018 at 02:35 PM. Reason: Typo
11-13-2018 | 08:02 PM
#2
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Joined: Jan 2012
Posts: 2,883
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From: New York & Indiana
First, verify verify fuel pressure. When the throttle is advanced, the fuel pressure should increase 3 or so psig to compensate for the increase in airflow and then settle back to normal pressure per Clark Garage.
Could be the fuel injectors. If that is the ditection the investigation shows, then have them cleaned and tested.
SouthBay Fuel Injectors Service is excellent
Could be the fuel injectors. If that is the ditection the investigation shows, then have them cleaned and tested.
SouthBay Fuel Injectors Service is excellent
11-19-2018 | 05:40 PM
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Joined: Dec 2017
Posts: 81
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From: Miami Florida
Update to this post: I changed the fuel filter and the car came back to life and RPMs were not a problem. I can only think maybe something got into the filter and clogged it while I was doing the change. Not really sure, but it's running better now and RPMs go up to 6,000 no problem now. I did drop a can of fuel cleaner in the car too, not sure if that had something to do with it or not, but I think it was just a clogged fuel filter. Done.
