intermitent problem

[matt-man]

Hi All,

Although the wedge is generally going really well, i have an intermitent problem which i would love to solve!

Basically, sometimes on cold start she misfires and the only way i can solve is to keep moving plug leads and dizzy etc and keep starting. Funny thing is, it cant be a bad connection as after she starts ot goes really well with no problems.

ANy ideas?

Auto choke maybe??

Cheers!

[jmorgan]

Mad idea but what is the throttle pot set to? I had an issue that had several symptoms but solved when I reset the pot voltage. It was way over. Things like an odd misfire fire when driving along but not always, eventually flooded completely when driving and stopped. Rare occasions flooding on start. Tick over varying etc.

Also, my cold start injector is a blanking plate. Never have a problem starting without it (OK, throttle pot now sorted).

I should add that after the flooding episode I stuck the previous set of plugs in and gave the flooded set a really good clean and baked to clear them up. I assume your plugs are OK?

[honestjohntoo]

matt-man said:

i have an intermitent problem ---- Basically, sometimes on cold start she misfires and the only way i can solve is to keep moving plug leads and dizzy etc and keep starting.

Fiddling the leads etc may be a red herring in that you are continually trying to start the engine at the same time and eventually it catches and runs. So its more likely to be a time related start-up mixture problem.

Unless you can establish that the sparks are being extinguished at the same time as the problem occurs ( See *** below), then the question is, is it a rich or weak problem?

Odds are its not rich enough due to a fault in the CSI or the CTS or in their associated wiring/connectors.

Do the appropriate component/component wiring tests for both:

http://www.vintagemodelairplane.com/pages/Rover_Te...

http://www.vintagemodelairplane.com/pages/Rover_Te...

(***) here is the smart process to aid ignition fault diagnosis.



Guaranteed Foolproof Intermittent Ignition Fault Finder -

Rig up two 4/5 watt 12 volt bulbs (or better still, 2V, 15mA LED's + 680 ohm resistors) on test leads into the cabin and connect one between coil +ve and earth and the other to coil -ve and earth. Mark the bulbs POS and NEG. Beware cables dont foul hot/moving parts.

Start the engine and observe:

POS sensing the ignition input voltage is permanantly on,

AND

NEG sensing the pulsed voltage across the Ignition Amplifier flickers in sympathy with engine rpm, or is dimly lit (LED's flicker better).

Now run the engine or drive the car and have a helper note what happens when the engine misbehaves.

If POS and NEG go out together there is an open circuit interruption of the 12 v feed such as a faulty wire/ignition switch,

OR

A short on the same circuit due to burned insulation.

If NEG comes full on the Ignition Amplifier (due to excess internal heat) or its associated wiring/earth has failed in open circuit mode,

OR

The pulsed input (ie Hall Effect or Reluctor) to the amplifier from the dizzy has failed or the associated wiring is faulty/shorting to earth,

OR

The Coil has failed in a short circuit mode (unlikely cos it would surely kill the amplifier methinks?)

If NEG goes out the Ignition Amplifier has temporarily failed in short circuit mode due to excess internal heat,

OR

the local wiring is shorting to earth,

OR

The coil has failed in open circuit mode due to insulation breakdown or internal heat

If POS stays lit and NEG show signs of flickering instability not sympathetic with engine rpm, then the Ignition Amplifier or its connections are on the blink.

(Please notify of errors/omissions.)

Edited by honestjohntoo on Wednesday 18th March 23:24

Edited by honestjohntoo on Wednesday 18th March 23:30

Edited by honestjohntoo on Thursday 19th March 09:44

Edited by honestjohntoo on Thursday 19th March 17:22

[RussWood]

If it is a flapper injection car then check the connector into the resistor pack (on mine '85 390 it is on the passenger side inner wing). The connector into this carries fairly high current feeds to the injectors so it needs to make a good connection for best running.

Only ever touch/wiggle one thing at once, this can help to locate problems. Make notes about what you touched and in which order so that the next time it happens you can try starting off with what worked last time.

If you are churning the engine over then if you suspect over-fuelling/flooding don't use short stabs at the key, the ECU starting enrichment logic turns off after 10 seconds churning so if you stop and start - it will enrich again.

Russ

[adam quantrill]

honestjohntoo said:

Guaranteed Foolproof Intermittent Ignition Fault Finder -

Sounds useful - I'm gonna rig one up tonight!

I still get the odd glitch with my setup and although I'm sure I'm eliminating faults, it's one at a time until it gets totally reliable, this will definitely help.

The good thing with the wedge is that you can quite simply set up a binnacle with the LED's in it, near the instruments and observable by the driver, and pass the 3 wires through an existing bulkhead grommet.

Edited by adam quantrill on Thursday 19th March 14:21