Go Back   AudiWorld Forums > Audi Models > Other Audi > Audi 90 / 80 / Coupe quattro / Cabriolet Discussion
Sign in using an external account
Register Forgot Password?

Welcome to AudiWorld Forums!
Welcome to AudiWorld.com.

You are currently viewing our forums as a guest, which gives you limited access to view most discussions and access our other features. By joining our community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join the AudiWorld Forums community today!

LinkBack Thread Tools Search this Thread Display Modes
Old 01-14-2014, 02:05 PM   #1
AudiWorld Member
Account #: 251689
Join Date: Feb 2013
Posts: 219
Default 1990 20V 90 fuel pump - Real Time alternatives?

So I'm getting a flat spot/hesitation on the freeway as I tip into the throttle, and the fuel pump started making noise a couple months back. I put in a new filter immediately but suspect it's the pump unable to keep up with 3500rpm. Though when I press deeper into the throttle it does not hesitate - so open to anyones input on that.

Was thinking of putting a new fuel pump on and looking for cheaper alternatives. I read somewhere that an ordinary Ford pump available anywhere is a perfect substitute to the $200 Bosch usually spec'd. Any input? Kinda under pressure because wanted to drive the Audi Thursday on a 300 mile trip but have another car. Perfect Quattro roads, so help me if you have a minute.

1990 Audi 90 Quattro 20V sedan.
IdahoDoug is offline   Reply With Quote
Old 01-14-2014, 02:17 PM   #2
AudiWorld Senior Member
Account #: 136523
Join Date: Oct 2007
Posts: 1,252

How certain are you about it being the fuel pump? it doesn't sound like it to me. I'd suspect either a vacuum leak, or bad injectors before the fuel pump.
"If you can see the tree you are about to hit, it is called 'understeering'. If you can only hear and feel it, it was 'oversteering'."
Walter Rohrl
Hybrid_Hatch is offline   Reply With Quote
Old 01-14-2014, 07:55 PM   #3
AudiWorld Member
Account #: 251689
Join Date: Feb 2013
Posts: 219

Yeah, I'm not convinced of the fuel pump either, with only item pointing to it being mere noise. Since it's one of the few key components I have not upgraded in the year since getting the car thought it would be a good time, and some chance it is the issue.

Injectors are all new (034's nice conversion kit) last spring, general major tuneup items as well. Everything save plug wires that you would think of doing to make a 23 year old car reliable for daily driver use has been done. Didn't do plug wires simply because of the shocking cost for the 20 valve set - my little protest...

Full throttle acceleration seems down a bit as well sometimes, other times it's normal. Fuel consumption slightly off, but not tracked precisely enough to say that definitevly. It's been going on for a month or more so not bad fuel.

I notice it when steady state driving at freeway speeds. In making those tiny pedal adjustments to match speed with traffic. Apply a tiny bit of gas and a faint falter occurs - not bucking or anything , just faintly felt hesitation. Sometimes I have also felt as I let up barely on the gas it will actually accelerate faintly. So behavior I would typically call a flat spot in the carburetor days. Thoughts?
1990 Audi 90 Quattro 20V sedan.
IdahoDoug is offline   Reply With Quote
Old 01-15-2014, 07:19 AM   #4
AudiWorld Super User
Account #: 153887
Join Date: Oct 2008
Location: Albuquerque,NM
Posts: 2,230

sounds like you might be getting flooded... but on the pump, if its making more noise then usual, it usually indicates that its reaching the end of its life and i would have one just in case yours fails and leaves you stranded in the middle of nowhere.
on the other problem, i don't think these two are related aether. look for a vac leak, i also assume no codes?
1993 Audi 90CS Quattro (loving it)
*(suspension and brakes)034 derling control arm bushings + alum-subframe bushings, 034 street density trans mounts+JHM SOLID” Short Throw shifter. B5 rear sport swaybar, B5 upper a-arms, solid VAP shock mounts + B&G springs + Bilstein sport shocks. EBC 3D front rotors + EBC green pads front and rear. 17" ASA's, head lights, aux gauges. blue plasma instrument cluster, A4 3 spoke steering wheel.
*(engine)replaced a motor at the end of 2008, gasket matched heads, ARP head studs, air box velocity stack, 4 to 3 wire MAF conversion, 18.5lbs flywheel with SPEC stage 2 clutch.
1975 VW bus (gone)
1973 VW Super Beetle (what was i thinking?)
1968 VW Bug (my pride and joy)
*2.5 inch front drop and disk brake conversion, *2110cc motor (in progress)new wiring harness,3 inch wider fenders all around, 195/45r15 front and 195/65r15 rear tiers
1991 GMC Sonoma RWD, manual, 4 banger (gone)
1979 Suzuki GS750EN with 31k original miles
1981 Suzuki GS750L (will be on a chopping block for a bobber)
1981 Yamaha XV920
1983 Yamaha XV750 (for g.f.)
1985 Dnepr MT10-36 (stolen)
1992 Dnepr MT11-32 (also stolen)
CRAZY_RUSSIAN is offline   Reply With Quote
Old 01-15-2014, 12:10 PM   #5
AudiWorld Member
Account #: 251689
Join Date: Feb 2013
Posts: 219

So a bit more info you may find useful. I realized this morning that the engine has for a long time exhibited a tendancy toward abrupt responses to the throttle at higher rpms, so this may be all that is happening at fwy speeds is what I'm about to describe. It's most obvious when the engine is cold, which is why I tolerated it figuring its a 23 year old engine and has some aged sensors that don't play well when the engine is cold up here in Idaho winter. Here's what its like.

Pulling away from the house with a cold engine, the throttle is very abrupt. A small accelerator movement pressing down makes the car lurch forward, and an equally small letup makes the engine instantly feel like it's been shut off completely from fuel and lurches the car slower. This hyper sensitivity goes on until the engine is warm. But even when warm, it tends toward this behavior such that at times it is hard to shift smoothly because the engine has this on/off feeling that makes clutch engagement tricky.

Thought I'd add that as I realized how bad that cold behavior had gotten while leaving the house this morning and it seemed logical the touchy throttle may simply be all that is happening on the freeway. Years ago I had a new K Jetronic Jetta that had that annoying throttle "tip in/tip out" behavior and the dealership and research confirmed was simply a part of the software that shut off fuel for fuel economy on coast that was a little aggressive and they could not adjust it. This feels like that only stronger.

So I guess this hyper throttle response would be the thing I'm wondering about - sorry for changing course a little and embarassed I didn't think this post through a bit before typing.

1990 Audi 90 Quattro 20V sedan.
IdahoDoug is offline   Reply With Quote
Old 01-15-2014, 12:10 PM
Audi R8

Paid Advertisement

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -8. The time now is 10:44 PM.

Copyright 2014 AudiWorld.com Audi Enthusiast Community

Personal Contacts

SEO by vBSEO ©2011, Crawlability, Inc.