Audi 100 5cyl cold start problem

Page 1 of 2  
Got a major problem here kindof i think. Got a 1991 Audi 100 with a 5 cylinder 2.3 litre fuel injected engine. you can crank it for ages and it will fire once or twice or sometimes
not fire at all and just keep cranking. This only happens when the engine (water) is cold. If I spray ether into the intake manifold it fires continually until I stop spraying but still will not start. I have removed two of the fuel lines going to the injectors and there is no fuel pumping up them but there is on the cold start fuel line. Im not sure if thats normal or not. but if i push up the lever thingy behind the air filter then fuel pumps very slowly up all the injector fuel lines. help help help!!!!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
My initial idea is to say the fuel injection relay might not be working the contacts wear out regularly (100k) and often don't give enough power to the pump, if it is working full on you should hear the pump kick in when you turn the ignition on for a couple of seconds before you start it. I had a similar problem on 100 CD similar engine set up 2226cc one. The relays are about 20 from german and swedish if I remember rightly, however it is possible to check this by actually bypassing this relay (not adviseable normally but just for test purposes, I ran my car on a wired switch for about two weeks until I managed to get a new one) as it's a safety feature to kill the pump once the engine is not "firing" rev check. You can use a suitable thick bit of wire between the sockets for the terminals once you work out after taking out the relay which ones are required to hard wire together. With the ignition on only you will hear the pump in the tank working. If it fires with this you need a new relay. IS the spray from the cold start very strong? The cold start is on a relay that bypasses the fuel distibutor if I'm right and will drain any pressure in it, or the fuel valve in the regulator is sticking. I assume you have not played with the mixture setting or dropped anything into the plate that regulates the fuel air mixture etc.
Give me a mail back if that doesn't help.
PAul

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I will try bypassing the relay but when i turn the key to on I can hear the fuel pump going and fuel is definately pumping, though im not sure how strongly. When cold starting are the 5 injectors supposed to be working or is it just the cold start injector that goes until it starts up properly? also can i just take out the cold start injector and turn it on and see if it sprays?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
All injectors should run on start up the cold start relay is only there to add extra fuel when its cold like a choke

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I also forgot to mention that the car does start every three days or so and once it starts and warms up it runs fine. you can turn it off and restart it but when it cools back down it wont start again for a few more days at least.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I also forgot to mention that the car does start every three days or so and once it starts and warms up it runs fine. you can turn it off and restart it but when it cools back down it wont start again for a few more days at least.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Okay cheap fix,
go and buy a new rotor arm for the distributor and if that fixes the problem contact bosch uk and get a new distributor. The shaft bearings wear out and the rotor arm contacts the contacts and heats up so much it blows the resistor as it cools and warms it contacts. If this is happening it is usually shown up as a crack in the dark brown resin they cover the resistor with. Have a look at it. You should also be able to rock the rotor shaft left to right if it is warn. Does this make sense?
Paul

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Makes sense but the engine is sparking perfectly without fail, unless the distributor tells the injectors when to fire? but when its cranking there is no fuel going up the injector lines from what i can tell, no fuel coming out of the metal round thing that all the fuel lines bolt into. (except for the cold start)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just thought of something else. Are all of the wires connected especially the idle valve. They could be corroded check them just pulling them off and refitting a couple of times might help.
The rotor arm actually usually actually works the other way it will start when cold but not hot, however I have had similar problems, I still think it might be the fuel relay. Don't forget that once it gets going it has to keep up the pressure and that takes more power to do so, so still try the bypass that I suggested mine also had the cold start issue. Just tapping the relay sometimes was enough during cranking to get it to start. If this has been going on a while it is likely to have carbon deposits etc. You could always take it out and take off the cover and have a look inside and see for yourself.
By the way if it is make sure you buy the 5 cyl relaynot the 4 cylinder I think there is an over rev cutout that will kill the engine at lower revs if you get the wrong one.
PAul

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I have a Haynes manual with test procedures etc if you would like me to scan it and mail it to you if what I have suggested doesn't help
Paul
Take out the spaces in the email address to email me directly

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
manual though is not accessible tonight, its in the back of the garage somewhere behind the car and I have to move the car to get at it and I've had a drink so it will remain there until tomorrow, I only have 2 inches either side of the car when I pull it out and I don't actually want to scratch it!
Paul

so
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
That scan would be great, wouldnt mind a wiring diagram, anyway ill check those things tonight when i get home from work and let you know. thanks Caleb.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Caleb, If you can hear the fuel pump running, and you're having a fuel delivery problem (manually lifting plate does not provide full flow to injectors), I would check the following: - replace the fuel filter - if fuel delivery is still a problem, there may be problems with the fuel pump pre-filter (a screen mounted on the intake of the pump - may get clogged with dirt), or fuel distributor problem. The Bentley Manual has a diagnostic procedure that you could follow, as well as Scott Mockry's site at: http://www.sjmautotechnik.com/trouble_shooting/ficis.html Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Well I have temporarily resolved the problem, I was just buying this car last night so I wanted to make sure the problem wasnt too terrible before i bought it. It turns out the cold start injector was not getting any power and to make matters worse i mustve knocked the distributor feedback plug out but i found that early enough. So i shorted the injector straight to the battery when cranking and for a short while afterwards and it worked flawlessly (although a slightly rich mixture for a few seconds) So now my only problem is to find out why there is no voltage to the cold start. The temperature guage is also not working which i will have to sort out. Anyone got any ideas on why it would stall when stopped and in gear with the brake on? only did this twice in a 40 minute drive.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I will also note that on the drive home it was absolutely wonderful. I love this car so far and for $850 NZD ($450US) I think it was well worth it. everything is in mint condition with full service history. 140,000ks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It still could be expensive 1991 ? but still only 80K Miles is nothing sounds like blockages, but I would also suggest you clean out the pipes that run the air / rocker cover / vacuum and especially the venturis (do it with solvent not poke things in there. If the Idle stabilisation circuit has blown itself and there could be melted wires back to it if any have been subjected to heat at any time and contacted earth there will be. The original circuits were built of discreet components and probably will be okay but the wires might have let go. There are extra wires on most of these cars for cruise control and turbo connections that flap about you may need to run new wires and this might help. Also check that the temperature sender units are working and the connections are good and clean. There is one on a 2226cc unit that sits under the thermostat that I have found troublesome that may be the one that activates the cold start injector (corrosion may be the only reason)
They do give up and you must buy the correct ones to replace them and they change massively on models over the range so get the chassis number to a dealer to make sure you have the correct ones.
Paul
Thanks for the extra feed back. It sounds like you're going through the exact same things I have been through with mine.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
IIRC The cold start might receive power from the starter solenoid. So check the wiring to there and also check to see that it does get power to that wire wihle the starter is operating. I am not sure where it grounds out if not through a thermostatic switch.
later, dave (One out of many daves)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It doesn't. but the cold start/ idle stabilisation circuit on older models relies on several thermostatic inputs on later models I am sure that a central control; cpu does it all and that should mean to uoi an dme scrap yard find one.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you are able to start and have the car "run" on ether, there is nothing wrong with the ignition system, but the car isn't getting any fuel.
How long is it since the fuel-filter have been changed? It might be clogged so badly that the pump cannot get enough pressure. On my car the fuel pressure should be around 4 bar.
Sounds like the fuelpump have gone bye bye. Usually you will be able to hear it going, but it isn't delivering enough pressure. Had the exact same problem on my car. A '93 Audi 100 2.3E.
I first tested the assuption with taking out the pump and cleaned it in a bucket of water while applying power to it. I then washed the pump with brake cleaning fluid in the same manner. I let it dry and reinstalled.
The car would then start, but the pump sounded like a hive of bees so I changed it for a new one. It cost me around US $300. Also: Change the fuel-filter if you change the fuel-pump. If not you'll have the same trouble in very short time.
--
snipped-for-privacy@dod.no
------------------------------------------------------------------------
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
if you were daft enough to run the fuel pump in a no lubricating medium such as water you deserve to have spent 30o bucks for doing so. It is a fuel pump not a water pump. You obviously wrecked the rubbers which are "tuned" to the fluid they are supposed to pump!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.