Re: Fuel pump cycling - Saab 9000 Bulletin Board - Saabnet.com
The banner above is an advertisment - if it asks you to download software, please ignore.
Site News - 7/1: Members: Log In to See Fewer Ads! | 5/28: SAAB Evolutions/TSN T-Shirts $14
[General | Members | C900 | 9000 | NG900 & OG93 | 93 | 95 | NG95 | 99 | Sonett | Vintage Models | Clubs | Other Cars | FAQs | Gifts | Member Photo Galleries | Member Directory | Classifieds | Manuals | *Buddy Registry | *Mileage Registry | Polls | What's New | Raffle | Photo of the Month | Sponsors]

9000 Bulletin Board
1985-1998 [Subscribe to Daily Digest]
(Search Author's Posts: e.g. Keyword:username)*Members Only

[Main 9000 Bulletin Board | BBFAQ | Prev by Date | Next by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: Fuel pump cycling
Like This Post: - Subscribe to Daily Digest for this Bulletin Board
Posted by Wayne [Email] (more from Wayne) on Tue, 28 Apr 2009 06:13:18 Share Post by Email
In Reply to: Re: Fuel pump cycling, Ari [Profile/Gallery] , Tue, 28 Apr 2009 03:41:15
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

. So when the car is first switched on, the fuel pump runs for a couple of seconds in order to build up some pressure. If the LH computer doesn't detect the engine spinning, it shuts off the pump. That's normal.
*** The pump does not shut off, it seems to run indefinetly.***

Yes, the pump cycling on and off with the key in the ON position is strange. A few thoughts. One, it might not be the pump you hear running.
*** It is the pump, I have pulled the fuel return line and it pumps fuel to back to the tank with each 'pulse' which is why I thought pressure was not being maintaned at the regulator***

You can always stick a voltmeter on the fuel pump fuse and see if the voltage is cycling on and off there. Two, there is a problem in the LH computer, and it is seeing noise on the input power line - it interprets this as the power being switched on again, so it runs the pump for another second or two, then shuts off. I'd suspect a bad ground to the LH computer. Three, your battery is low - with a low ON voltage (engine not running), the LH computer may be seeing that low voltage as the key in OFF, or some other load on that power bus is cycling and pulling the voltage up and down, and the LH computer turns on the pump for a second each time.

If you've got voltage problems, fix the charging system.
*** The alternator is bad but this symptom (we thought) appeared before the alternator went bad. Maybe you are right and the alternator/low voltage is causing this problem. The car is running strictly off a fully charged battery***

Thanks for the help Everybody!!

posted by 70.89.13...

Posts in this Thread:
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup
Post a Followup

No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.

Name: Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
E-Mail: (Optional)
Re-Enter E-Mail: (Confidential & Secure - Not revealed to other users!)
Note: Please check your spam folder for BB responses.

Subject:

Posting rules are simple - No for sale/wanted ads may be posted here - use the site classifieds.
You may not cross-post your message to multiple BBs.
Not permitted: political/religious topics and being disrespectful (personal attacks, insults, etc...).
 Site Members do not see any red text, inline ad links, bottom of page anchor ads, box ads, or anti-spam check.

Message: (please no for sale/wanted classifieds - post those in the Saabnet.com Classifieds)
Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).

Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post above, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).
Optional Link: (e.g. http://www.saabnet.com/)
Link Title: (Optional)
Optional Photo/Image Link: (e.g. http://www.saabnet.com/img.jpg)
Photo/Image to Upload: (Please be patient while file uploads)



StateOfNine.com
SaabClub.com
Jak Stoll Performance
M Car Covers
Ad Available

The content on this site may not be republished without permission. Copyright © 1988-2024 - The Saab Network - saabnet.com.
For usage guidelines, see the Mission & Privacy Notice.
[Contact | Site Map | Saabnet.com on Facebook | Saabnet.com on Twitter | Shop Amazon via TSN | Site Donations]

Random Saabnet.com Member Gallery Photos (Click Image)
This is a moderated bulletin board - Posting is a privilege, not a right. Unsolicited commercial postings are not allowed (no spam). Please, no For Sale or Wanted postings, SERIOUSLY. Classifieds are to be listed in The Saab Network Classifieds pages. This is a problem solving forum for over 250,000 Saab owners, so expect to see problems discussed here even though our cars are generally very reliable. This is not an anything goes type of forum. Saabnet.com has been a moderated forum since 1988. For usage guidelines, see the Saabnet.com Mission and Purpose Page. Please remember that you are not anonymous. Site Contact | Site Donations | Other Sites by SP - Poverty2Prosperity.org | Run Club Menlo Park | ScreenBot


Site Members do not see red text instructions, bottom of the page anchor ads, or box ads.
Click here to see all the Site Membership Benefits!