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Topic: Erratic tacho (Read 668 times) |
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geoff_bateman
Newbie
2.9 12v Estate
Posts: 16
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Erratic tacho
« on: Feb 23rd, 2010, 9:46pm » |
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Just aquired a 95 N plate V6 12V Ultima Estate after 8 years of happily owning a Granada Scorpio. When I got it there was a fairly serious ignition problem requiring RAC intervention 3 times on the way home. Investigation revealed a dubious ignition module (replaced), Hego fuse blown. With a bit of prodding around following advice from others checked the engine harness and it was the worst condition that I have ever seen in 40 odd years of playing with cars.
Rebuilt and checked the harness (it had been shorting out the ignition module out put to the EEC unit), replaced the ignition module, replaced the dissy cap and rotor arm, hego sensors and plugs and leads. Now starts and run well. However, one thing is still not right. The tacho was erratic when I bought it and I assumed that this was probably due to the ignition module/harness problems. However the problem persists. I have done the instrument panel check (thanks forum) but it is difficult to judge the pulse count number against the tacho as it is moving so much, but at times the tacho goes to zero even though the engine is doing 3000+ rpm.
Does the tacho pulse input come from the ignition module as per in the Granada V6 12V or is it fed from the EEC unit?
Seeing as the harness to the EEC was shorting this has probably produced error messages in the EEC, will these automatically rectify themselves or do I have to get someone to interogate the unit and cancel them?
Sorry this is so long winded but I thought that fullest info would be best. THANKS
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Jonnycab
Senior Member
Former owner of 2.3 Ultima Facelift saloon
Posts: 3900
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Re: Erratic tacho
« Reply #1 on: Feb 24th, 2010, 12:18am » |
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As far as I know, the tacho gets it's signal from the alternator 
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gozz
Senior Member
Been around awhile
Posts: 3475
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Re: Erratic tacho
« Reply #2 on: Feb 24th, 2010, 1:16am » |
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geoff.
I think Jonnycab is correct as far as the cars with EEC V go,but the 12valve with coil and distributor,I think takes tacho pulses from the ignition as on the late Granada.
GOZZ.
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Jonnycab
Senior Member
Former owner of 2.3 Ultima Facelift saloon
Posts: 3900
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Re: Erratic tacho
« Reply #3 on: Feb 24th, 2010, 2:23am » |
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Gozz, I hope your feeling hungry, as Snoopy may still have some humble pie left over from this post a couple of years back  ....
Rev counter stopped working ....looks like the 12V tacho is supplied by a black/white wire coming from the alternator 
Geoff...click on the blue writing to view the full post
P.S.....It took me so long to find this old post that I'm nearly out of breath
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geoff_bateman
Newbie
2.9 12v Estate
Posts: 16
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Re: Erratic tacho
« Reply #4 on: Feb 24th, 2010, 8:44am » |
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Thank you everybody for the prompt and informative response. I am extremely impressed with this forum, it is very "grown up". Amazingly informative and helpful.
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Highlander
Moderator
Expert
13 Scorpios, XR4x4, Suzuki SJ413 for off road :)
Posts: 8244
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Re: Erratic tacho
« Reply #5 on: Feb 24th, 2010, 9:40am » |
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on Feb 24th, 2010, 8:44am, geoff_bateman wrote:| I am extremely impressed with this forum, it is very "grown up". |
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We have to behave otherwise Evil Snoopy will get us
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on Oct 17th, 2011, 12:35pm, Simmo wrote:I give up !  Too much for an old boy!  |
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Tompion
Administrator
1997 2.3 Ultima estate.
Posts: 2918
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Re: Erratic tacho
« Reply #6 on: Feb 24th, 2010, 9:57am » |
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Assuming the table is correct on the page for instrument reset it says for pulses “This check allows the engine speed signal coming from the alternator, (12V V6, 2.5 TDi) or the EDIS (all others)”
http://www.fordscorpio.co.uk/instreset.htm
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ABS multiplug wheel sensor pins MK IV or MK 20
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gozz
Senior Member
Been around awhile
Posts: 3475
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Re: Erratic tacho
« Reply #7 on: Feb 24th, 2010, 10:22am » |
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Humble pie suitably shared  and indeed the proof of the pudding is in the eating,I changed a squeaky 12valve main drive belt this morning,and in view of the foregoing posts,ran the engine without the belt,and lo and behold no tacho
Best forget Granadas methinks !!
GOZZ
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Jonnycab
Senior Member
Former owner of 2.3 Ultima Facelift saloon
Posts: 3900
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Re: Erratic tacho
« Reply #8 on: Feb 24th, 2010, 11:59am » |
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Makes a change Gozz ....it's usually me that eats all the pies on here
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geoff_bateman
Newbie
2.9 12v Estate
Posts: 16
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Re: Erratic tacho
« Reply #9 on: Feb 24th, 2010, 3:17pm » |
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Jonnycab, top bloke, thanks a lot. Been out and checked and some previous person must have had the connector off the back of the alternator and not only was it not on very far, it was also loose. Nipped it up, applied WD40 and refitted correctly, tacho sorted. Thanks once again.
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