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It is not the AFM but what could it be?

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Hefeweizen
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It is not the AFM but what could it be?

Post by Hefeweizen » Tue Apr 03, 2018 5:49 pm

I thought that my AFM (Part #13621359641 -Bosch #0280203002) died since it looked like it no longer sends a signal to the double relay (1979 M90 L Jet engine) and hence the car does not run anymore.

I do have continuity from the battery to the fuse box and again to the double relay and continued from the double relay to the fuel pump. If I jump the two connections by the double relay I get a humming from the fuel pump. I understand that the AFM is supposed to send a signal to the double relay which kicks on the power that gets the engine going when the flap opens in the AFM and it's also supposed to click. Well, it does click but still no power to the pump. The thought that the DME is busted, since it smelled burned had crossed my mind but according to the diagram the DME has no say in this.

Had the AFM open. Everything looked OK. With the ignition on I got power to port 39 and when I open the flap power goes over to 36. So the micro switch seems to work. I checked continuity from both wires to the double relay and we have continuity. I have an old double relay in and also connected the new relay and still nothing. Lack of ground on 6 maybe? Is there any other item that would enable the power to the pump?

So from the way it looks the AFM is good. I get 12V to the AFM and when the flap is opened 12V go out. I measured at the connector by the relay. I can also hear the click at the relay. There is ground at #6 at the AFM but only when the ignition is on. So from the way it looks the circuit is good there. Does the DME provide input to the fuel pump power cicruit?

I ordered a DME, it arrived and I could not wait to plug it in. Plugged it in and measured for voltage at the pump. YES!!!! I had what it takes! I put the thermostat housing back in (had to change the thermostat since it was stuck in the open position due to the PO sticking a screw in there). Had some complications since some of the screws broke due to old age and me beasting around (unrelated issue). Strange thing is that for a while I have power at the pump regardless of ignition on or off and flap at AFM open or closed. Did not last long though).

The car sat there for a while and when I tried it would not start anymore nor did I have current going to the pump. If I apply 12V at the pump (bypassing everything going straight from the battery to the pump), the car runs fine and as soon as I disconnect the power.
Last edited by Hefeweizen on Thu Apr 19, 2018 2:04 pm, edited 2 times in total.
Rainer
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Brucey
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Re: AFM Testing

Post by Brucey » Wed Apr 04, 2018 7:04 pm

IIRC L-jet AFMs (not LE-jet ones that are fitted to 628 models) simply contain a microswitch that powers the coil on the fuel pump relay whenever the flap moves even slightly. I've not BTDT but the switch is probably under the cover along with all the other electrical gubbins.

I would be very surprised indeed if

a) a duff switch couldn't be resuscitated by use of contact cleaner and/or
b) the switch itself couldn't be replaced eg with a standard industrial part (if it isn't one already)

Also I would say this sort of thing is quite likely to be detailed somewhere on the firstfives website.

cheers
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Hefeweizen
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Re: AFM Testing

Post by Hefeweizen » Wed Apr 04, 2018 7:06 pm

Thanks Brucey! Would you or anyone else for that matter know if Bosch #0 280 203 002 and Bosch # 0 280 203 011 are interchangeable?
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Brucey
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Re: AFM Testing

Post by Brucey » Wed Apr 04, 2018 7:19 pm

further to the above I found these pics that may be useful;

Image

shows L-jet afm pinouts (NB for 7-pin L-jet AFM, not LE-jet model) and below is what the inside of a 7-pin L-jet AFM looks like.

Image

AFAICT the blue arrow indicates the arm that works the fuel pump switch and the red arrow indicates the fuel pump switch contacts. If yours is as depicted it looks like a fairly easy fix; the worst bit will be removing the AFM cover I expect.

I found the pics using a search engine but further digging shows that they come from this article about L-jet fuelled rover V8 engines as fitted to older Morgan plus 8 models;

http://www.gomog.com/articles/AFMadjust.html

which is very useful even if I don't entirely agree with some of the comments therein.

hth

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Hefeweizen
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Re: AFM Testing

Post by Hefeweizen » Thu Apr 05, 2018 11:42 am

Thanks again Brucey! I'll check on this over the weekend. I really got a laugh when I saw #8
Rainer
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Hefeweizen
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Re: AFM Testing

Post by Hefeweizen » Fri Apr 06, 2018 11:46 pm

Finally got the AFM open. Everything looked OK. With the ignition on I got power to port 39 and when I open the flap power goes over to 36. So the micro switch seems to work. I checked continuity from both wires to the relay and we have continuity. I have an old double relay in and also connected the new relay and still nothing. Lack of ground on 6 maybe. Is there any other item that would enable the power to the pump?
Rainer
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79 633CSi (Red Euro, Project)

"If you think a good European mechanic is expensive, try a bad one!"

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Re: AFM Testing

Post by baders » Sat Apr 07, 2018 1:39 am

Are you showing voltage present at the fuel pump relay from AFM pins 36 or 39 ?
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Hefeweizen
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Re: AFM Testing

Post by Hefeweizen » Sat Apr 07, 2018 8:54 pm

baders wrote:
Sat Apr 07, 2018 1:39 am
Are you showing voltage present at the fuel pump relay from AFM pins 36 or 39 ?
baders wrote:
Sat Apr 07, 2018 1:39 am
Are you showing voltage present at the fuel pump relay from AFM pins 36 or 39 ?
From the way it looks the AFM is good. I get 12V to the AFM and when the flap is opened 12V go out. I measured at the connector by the relay. I can also hear the click at the relay. There is ground at #6 at the AFM but only when the ignition is on. So from the way it looks the circuit is good there. Does the ECU provide input to the fuel pump power cicruit? I'lll check that later after I am done with the thermostat
Rainer
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79 633CSi (Red Euro, Project)

"If you think a good European mechanic is expensive, try a bad one!"

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Hefeweizen
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Re: AFM Testing

Post by Hefeweizen » Fri Apr 13, 2018 1:51 pm

I ordered a ECU which arrived yesterday. Could not wait to plug it in. Plugged it in and measured for voltage at the pump. YES!!!! I had what it takes! This weekend I will put the thermostat housing back in (had to change the thermostat since it was stuck in the open position due to the PO sticking a screw in there). Had some complications since some of the screws broke due to old age and me beasting around. Should have Igor running tomorrow.
Rainer
85 635CSi (Silver, Daily Driver)
79 633CSi (Red Euro, Project)

"If you think a good European mechanic is expensive, try a bad one!"

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