Rev Counter going to full then zero

[Roy]

Hi
I have a 1997 1.9td and when I start it the rev counter bounces to full then goes back to zero, the car starts but KNOCKS like hell.
I switch it off then turn the key again not waiting for the preheater light to go out and MAYBE the rev counter will work properly, sometimes I have to do it 5 or 6 times before the counter stays at 10 then it ticks over properly [ No loud knocking].
I have looked in the 10 pages searching under rev counter but could not find anything resembling my problem. So I was wondering have ANY of you people have had a similar problem.?????
Plus sometimes the speedo wont work and I would be driving along and all of a sudden the speedo jumps up and starts working OK

[teamster1975]

Problems with the rev counter &/or speedo are mostly down to dry joints on the dash pcb; that wouldn't explain the knocking though...

[steve_earwig]

Assuming both are related I'd head for the RPM sensor (clutch bellhousing)

[omega]

i think the knocking is normal when you try to start without the glow plugs[my old 405 was the same]
as you say when you start it as it should theres no proplem

[Roy]

Steve.
When you say RPM Sensor,??? what do I look for mate, and should it be replaced or is it fixable.???
Thanks to all you decent people that replied, to try and help me out.

[steve_earwig]

It's on the bellhousing, rubber grommet, 1 bolt (says Haynes). I'm not sure what could go wrong with it tho, sometimes ok, sometimes not maybe you should check connections...

[Terryc]

Had nearly the same symptoms on my old 306 1.9d, exept both the rev counter and speedo would shoot over to full for a few seconds after starting, then drop back to normal.

Turned out to be a dodgy battery of all things.. Changed it, everything went back to normal!
No heat in the glowplugs would explain the lumpy running on startup, mine would judder like mad, smoke like mad, then settle after a min.

[Roy]

This was really pi**ing me off, so I thought I'd spend some time to TRY and sort it, cos to tell you the truth my bottle went with the soldering part. No way do I think I could do it.
Anyhow I was under the bonnet and I saw a wire that appeared to have melted as it appeared to go over the rocker cover,from the main loom I could not find the other melted end, so I went up the stealers said I would buy the wire but where does it go. 1 Parts Salesman and 1 Auto electrician later nobody could tell me where it went, so I left my mobile # and the electrician said he would check later in the manual. 3 hours later he phoned, saying he thought it went to #1 injector I checked and low and behold it went to #2 but was well hidden with vent pipes, I phoned Dutton Forshaw saying I would buy the wire, they quoted me £230 for the complete injector as the wire does NOT come seperatly. "UP THAT" so I stripped 2 big vent pipes and a fuel line stripped what little wires were left and spliced a piece in, with my fingers crossed as I was told they were 1 Black and 1 White but BOTH wires were White. and guess what, It works it's been 4 days now and every time I start the beauty, the rev counter behaves normal.
So Thank you to everybody the took the time to try and help.

[Welly]

That is brilliant!

That repair, at a Dealer, would have cost over £400.00

These problems are alomst always really simple - it's just finding it that's the problem.

[steve_earwig]

Smoking! Well done yung maaan

Faults usually are one thing, the problem's always first the diagnosis, then we move on to how much of the car you have to buy along with it and eventually which precious metal/type of gemstone Pug reckon it's made out of

"oooh, real gold that injection loom, they just forgot to put the hallmark on..."