CIS troubleshooting

rob hod rob3 at
Mon Nov 12 20:43:43 EST 2001

    In what way did the car stop working. Has it stood a while, did you do
some maintenance and then it wouldn't start, or did is it in normal usage
and just refuse to start one morning?

    Control pressures sound a bit high , but not enough to stop it running.
High control pressure = lean mix, so CSV should help to get you started or
lead to some spluttering at least.

    If the FPR was inop then you would have no pressures anywhere CSV ,
control pressure or anything.

    IME its usually ignition that leads to unexpected no-start conditions.
Apart from FPR, injection usually gives signs of impending doom. Have you
checked and double checked the ignition lead sequence ( is it possible
they;ve got mixed up) also is the ignition timing right? and have you
checked the condition of the T-belt - is it worn out and jumping teeth?

    Finally check your compression, although you wouldn't expect it to
disappear all at once!


rob (who also bought a JC whitney FP gauge and wept at the shipping and duty

----- Original Message ----- > Message: 15
> Date: Mon, 12 Nov 2001 13:50:39 +0000 (GMT)
> From: Graham Thackrah <gthack at>
> Reply-To: Graham Thackrah <gthack at>
> To: quattro at
> cc: "Paul R. Cole" <bdssprc at>
> Subject: CIS troubleshooting
> Hi List,
> Any pointers gratefully received.
> My 1985 UK 90 quattro with CIS basic (after Probst) doesn't start. All the
> ignition components check out fine (coil resistance, hall sender, and
> ignition control module all pass the tests outlined in Haynes). You can
> pull plugs, ground them and they have nice juicy sparks when you crank the
> engine too:)
> I just got hold of a FP guage and system pressure is just a bit below 5
> bar. Cold control pressure was above 2 bar though, and I think this is
> supposed to be lower (1.5 nominal?), it was about 10 celcius when I tested
> it, and the engine was stone cold. With the ignition on but the car not
> running control pressure rose slowly to about 3.5 to 4 bar. Does the
> heater in the warm-up-regulator need the engine to be running, or just the
> ignition on? Before I tried that it seemed that control pressure was
> slowly rising anyway, with no power to the warm-up-regulator, could I have
> been imagining that or is it supposed to do it?
> When control pressure regulators fail, do they fail and give a higher or
> lower than spec control pressure, or does it depend on their mode of
> failure?
> I can see if the cont. press. is too high then the car would be running
> too lean to start, but my car doesn't make _any_ attempt to start, no
> stuttering or anything. I pulled the FP relay and opened it up to find
> some dodgy (tm) looking contacts there, possibly shorts, so it could be
> that causing my troubles, should the car start with the FP jumpered and no
> FP relay fitted? Also, would it be ok to refit the FP relay without its
> cover and see if it flips ok when starting? Or should I just check the FP
> gets 12V on cranking with the relay in place?
> After stopping the pump, the residual pressure is just below 3 bar, which
> I think is ok, and it kept this for at least 5 mins, the fuel pressure
> accumulator is certainly not marginal.
> I also think I checked all my air/vac hoses too (its got new vac lines
> throughout, only the breaters are not new but I think they're ok), even
> put hose clamps on some that never had them before when the car used to
> run. I also just replaced all the seals and seats on the injectors (the
> old ones were very marginal), but didn't check the spray pattern of the
> injectors, or even if they sprayed at all. Of course, I could have fixed a
> huge vac leak at the injectors and now the car's running too rich to
> start...!!
> With the air intake boot off the air metering plate doesn't stick if you
> lift it and you can feel residual control pressure resisting its upward
> movement, when you drop it it bounces once or twice then comes to rest.
> When you crank the engine the cold start valve fires a lovely text book
> cone of fuel, but I didn't check if it stopped after c. 2 seconds.
> There is fuel in the tank too;)
> Any other ideas? My first priority is to confirm the FP relay is ok, so I
> may try and replace it with a known good one and see if it makes any
> difference.
> Cheers in advance,
> Graham.
> P.S. Hi Paul, hope you remember this, sorry it took me so long but I ended
> up shipping JCWHitneys FP guage over as you can't get FP guages for much
> less than several hundred pounds over here, and no, don't ask how much it
> cost to do that, it was still cheaper... just! I also got a copy of
> Probst, and got the basics, but I'm still totally stumped with this one.

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