Intermittent start problem
05-24-2007, 04:01 AM
#1
8th Gear
Thread Starter
Join Date: Jun 2005
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
Intermittent start problem
I am pretty sure this is related to a fuel pump issue, but correct me if Iam wrong. The beast (1987 911 Turbo-all stock) will start when it wants to and I am not sure if it is a pump relay (that's my guess) or something else. What happens is generally when I get in and crank it, it will either start right up with no hesitation, or not start at all. I have noticed that when it does start I can hear the fuel pumps running before it starts. Are the pumps supposed to be running continuously when you have the key in the on position before the engine is actually cranked? Or do they run momentarily until pressure builds and then cut back in when the car actually starts? Is this type of problem usually indicative of a bad fuel pump relay? I am afraid to take this thing on the street for fear of getting stuck somewhere. Thanks for your help.
05-24-2007, 04:44 AM
#2
Intermediate
Join Date: Aug 2005
Location: Gothenburg, Sweden
Posts: 37
Likes: 0
Received 0 Likes
on
0 Posts
I agree, it sounds like a fuel relay. I had the same problem on my 87 930 once and it turned out to be just bad connection on the fuel pump relays. I just "expanded" the pins on the relay to get a tighter fit and I have never had the problem again. The pumps are supposed to run for a while when you turn on the ignition in order to build pressure and then the start again when you crank. Hope it helps.
/Mattias
/Mattias
05-24-2007, 10:55 AM
#3
Pro
Join Date: Jan 2002
Location: Wisconsin, formerly of Boston
Posts: 571
Likes: 0
Received 1 Like
on
1 Post
halfbad,
No, you should not hear the pumps running when the ignition is in the 'on' position. There are a few conditions that must be met before the pumps are allowed to run. One, the ignition is in the 'on' position. Two, the engine is drawing air through the CIS metering system. That is, the air metering plate has been drawn down due to engine air pumping action. Third, the overboost switch is in the closed position.
That whining you hear may not be the pumps at all, but the CDI ignition. If you think its the relays, you may use the black relays as a short term solution to see if the symptoms change.
No, you should not hear the pumps running when the ignition is in the 'on' position. There are a few conditions that must be met before the pumps are allowed to run. One, the ignition is in the 'on' position. Two, the engine is drawing air through the CIS metering system. That is, the air metering plate has been drawn down due to engine air pumping action. Third, the overboost switch is in the closed position.
That whining you hear may not be the pumps at all, but the CDI ignition. If you think its the relays, you may use the black relays as a short term solution to see if the symptoms change.
05-24-2007, 02:04 PM
#4
Drifting
Beyond the other good advice that you've been given so far, the only time I ever encountered a fuel delivery starting problem was due to a fuse making a poor connection in it's saddle/holder. In addition to the fuel pump relays, there is also a fuse on the luggage compartment panel. I'll try to snap a picture tonight. In my case, the wiring to this fuse was old, and the conacts were in horrible shape. What I actually did was wire a more modern in-line fuse kit from a local autoparts store in place of the faulty section on my fuse panel. Never had another problem.
...KNOCK ON WOOD...
...KNOCK ON WOOD...
05-24-2007, 02:11 PM
#5
8th Gear
Thread Starter
Join Date: Jun 2005
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
Great advice guys. I will look at these components tonight and hopefully come to a conclusion this weekend. With a little luck we will be tearin' it up in the next week or so. Thanks one and all.
