rough idling PI

[Casar66]

Hi there,

I had toe replace the spherical bearing of my MU. After changing my CR does not run as smooth as it did before. the symptoms are similar to a light misfire, you can feel the vibrations. Calibration of the MU did not help. I have checked the injectors, all works well (means after pulling them out while the motor is running the pictures are all the same, pulsating and spraying). I have again checked the position of the diaphragm and the datum link arm. the overfuel lever is free. Then I have checked the timing and the plugs. All work, plugs of cylinder 1 and 2 are slightly brighter than the 3-6. I have changed the rotor arm and controlled all wirings and connections. I am using a petronix II instead of the normal contact ignition. I have done quick 100mls, I do not miss power, I guess at higher revs it becomes better, but not sure. The consumption is 12 liter on 100km. What else, any idea?

Carsten

[DaveN]

I Would say the airflow through the throttle bodies require adjusting. Ideally with an airflow meter something like ........

eBay item number 272202975686.

Have a look on your local eBay.

 

Dave

[Casar66]

I dissambled and put the MU together again, checked every connection of the ignition, wobbled here and there. so did the same procedure than yesterday an dated days before. Only difference: I pulled and pushed back the top of the crash-switch. But now it runs smooth again. Hm, feels not that trustworthy.

[Waldi]

Carsten,

I assume you refer to the inertia switch?

If you pump is a Bosch pump it will draw a high current, like 10A or a bit more.

A good modification is to use a relay, this will also relieve your ignition switch and at the same time reduce the voltage drop to the fuel pump.

If in doubt about the inertia switch, there are several old posts on this forum.

Waldi

[Casar66]

Hi Waldi,

yes, I meant the inertia switch. Don´t know if it is not working proper but is it possible that it could cause a rough idling? I am thinking a long time to replace that inertia switch with that relay from Hella 4rp 008 189-41. Is is that what you do mean?

[barkerwilliams]

On my car rough idling has always been butterfly adjustment on the throttle bodies. Not easy to get right though.

 

Alan

[Waldi]

Carsten,

I would not see why a poor inertia switch would cause rough idling. You can easily check by connecting the 2 wired (bypassing the switch) and see if it makes a difference.

 

Regarding the relay: you cannot replace the switch by a relay, but can add a relay, similar way relays are used for front lights and electric fans.

Best to use one type of relay for the different users, if you have more of them.

I have 30A relays with integral fuse for lights and pump, 3 in total.

The relays for the lights have separate fuses for each filament.

 

As Alan says, TB adjustment is more likely the cause.

 

Waldi

[Casar66]

ah, now I got it with. I thought there is a relay which would replace the inertia switch. I use also relays for lights, pump, overdrive.

 

back to the idle: I do not think that adjustment of TBs is the cause, because as I wrote in #3 now it runs smooth again, the idling nice not rough anymore. But I do not why.

[Waldi]

If it now runs smooth again, I would leave it like that.

If you suspect the inertia switch, see if you can open and clean it or install a new one, to eliliminate re-occurring.

Installing a relay is recommended too, but I would first measure voltage at the pump, both at pos and neg connection (both measurements to a good earth, best the battery neg. poole.

Then compare with the battery voltage, all when running idle.

Waldi

[barkerwilliams]

Why not strip and clean up the inertia switch as per this guide:-

"http://www.grampianstags.net/inertia.htm"

 

Yes Bosch pumps need more current and fitting a relay assists the pump struggling and running hotter. Wire a relay with the inertia switch in the solenoid side of the relay not on the load side of the wiring. This reduces current flow through the inertia switch.

 

Whatever fuses you car has fitted always carry a 15amp modern blade fuse, this neatly connects to the two wires on the inertia switch if you have need to bypass the inertia switch on the road.

 

 

Alan

[astontr6]

Carsten,

I would not see why a poor inertia switch would cause rough idling. You can easily check by connecting the 2 wired (bypassing the switch) and see if it makes a difference.

 

Regarding the relay: you cannot replace the switch by a relay, but can add a relay, similar way relays are used for front lights and electric fans.

Best to use one type of relay for the different users, if you have more of them.

I have 30A relays with integral fuse for lights and pump, 3 in total.

The relays for the lights have separate fuses for each filament.

 

As Alan says, TB adjustment is more likely the cause.

 

Waldi

+1 Bruce. But note not all Bosch pumps draw a high current? Mine only draws 7 amps also it must have a good earth. the earth behind the rear inner wing card board trim is nitrous for going rusty? The wire size is important too, s/b 2 mm sq. 25 amp rated. Triumph modified the wire size in summer 72! I think? Contacts in inertia s/w, need to be cleaned and polished with 1000 grit wet and dry every so often. Butter-flies can only be balanced with an air flow meter in my view!

 

Bruce.

[Casar66]

find out that the injector of cylinder #1 did not work proper, sometimes it works, sometimes not. Replacing the injector (with and old one with new viton seal) made it not really better. Only if a replace the injector again with a brand new injector works for since roughly 100mls then.

I am wondering why the first replacement did not work. the viton seal is new and the injector looks more or less used but ok. Not sure if the injector is really the cause of my problems. I remember first time when the came up the injector #1 has worked. Are there other points than the seal that devide good injectors from bad ones?

Carsten