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Technical Won't Idle after Cam Belt Change

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Technical Won't Idle after Cam Belt Change

hot_fiat

hot_fiat

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Jun 13, 2005
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Blyth, Northumberland
Hi Guys,

my 20v Marea has decided that it will refuse to idle or rev after having its cam belt changed.

What happened is this - followed Pete's guide & marked everything up, realised that in order to change the idlers and tensioner I'd have to shove the engine over a bit so took it off its mounts and pushed it right over toward the nearside. Changed the tensioner (for a nice spangly cast alloy one), idler and new belt. Fired her up & immediatly sounded like a bag of spanners. Ran onto fast idle for 2-3 sec then drops to slow idle & stalls. Try revving & get nasty backfire. Wont go above 3000rpm

Immediatly suspect timing, so pick up set of cam locks. Lock cams & follow FIAT procedure, re-fitting belt & slackening off pulleys to set timing using locks. Fire her up - exactly the same. :cry:

I have my suspicions its a sensor issue. Possiblly the cam position unit, or perhaps the MAP sensor.

Its a 99V with the 155bhp lump & fully electronic throttle.

Any ideas? :confused:
 
It fires up - revs up to fast idle (~200rpm) then attempts to settle at slow idle & stalls. No flashing lingts, nothing. Press the accellerator & it revs up to 3k then splutters, occasionally backfires & stalls.

The timing is bang on as far as I can see. Even if it were 1 tooth out it should still idle. Think I may have to swallow 14 years of pride & take it to a grarage as I don't have diagnostic equipment.
 
There may be a crank position sensor you have disturbed. Umlikely to be engine earthing as the starter motor current must be running to ground somewhere, however easy enough to check this with a piece of wire from the engine to any earth point. :bang: I was in this position with the hreater fan outputs from the ECU when I joined the forum, I got one working and left it at that figuring why pay £200 and get the car back totally ****ed. Is there an independant with the kit near you?
 
Alot of cars wont start without cam sensor signal....also 1 tooth can make it cut out,done 2 bravas recently with exactly same symptons as you have(without the backfire)........both were incorrectly timed.
 
well, finally got around to re-timing the engine. Was very careful, did exactly what fiat's own manual says: - lock cams, remove belt, find tdc, loosen cam pulleys, re-fit belt, apply tension, torq up pulleys, remove locks, spin twice by hand, re-tension, refit covers & ancilliaries.

and....

it does the same. :cry:

decided it must be a sensor, so started to unplug each one systematically & see what that does. Started with the air mass sensor, which turned out to be a good choice as the engine immediatley fired correctly.

But... in doing the timing it was impossible to get the exhaust cam pulley and crankshft pulley timing marks to line up with the markings printed on the belt - even with both pulleys loose. Is it usual for the marks to be adrift? :confused:

I really wish I'd driven the bleeding thing down south & got a specialst on the case. Done all sorts of fiat cam belts in the past (Punto HGT & sporting, Cinq, 131, Tempra, Alfa 156) & never ever had this kind of bother. What a complete nightmare! :bang:

so what should I do - re-time it AGAIN, or go down the replace-the-air mass meter route???
 
How much do the marks miss by? If the pulleys are still on the same cog it will be the best you can do. It's very unlikley that the air mass sensor failed just at the moment you changed the belt.Prolly the ECU is going into a limp home mode that happens to sound a lot better. Did you cut the old belt? If not you could try offering that up again and see where the sit, In fact even if it is cut I would gaffer tape it back together and check at this stage in the proceedings.
 
bulldog5046 said:
i think your TDC is out personally, have you used the case markings?
Click to expand...
You can check TDC thru the plug ,ole of course if you want to. I would take all the plugs out so it turns over easily and then when check what you believe to be TDC against the marking you are using with a wooden dowel through the plug opening.Make sure you are rotating the engine in the direction it drives.This is not going to be a walk in the park as I hate changing the pugs on my car, aly thead completley buried under all that OHC stuff...
Thinking about this...
You could just loosen the other plugs to spin the engine, or even leave tham as you are only interested in the compression stroke on no. 1
 
Last edited:
I used the TDC of cylinder #1 - established through use of a dowl down the plug hole. Gonna see tomorrow if I can check tdc using the tdc sensor hole and a mirror at the back of the crankcase.

old belt's hanging on the wall in the garage, I even counted the number of teeth it had to make sure I hadn't been sent the wrong one! I may try fitting it back on to see if things line up. It's such a ball-ache to get on & off though. :(

Wouldn't be so bad if the Cinq hadn't taken a huffy fit and split it's fuel tank in two.
 
The only other possible is if the camshafts have moved. Did you mark them with paint or a scratch before removing the belt( i know this is a bit late 4 this comment...) but if you have the old belt you can recover this.
 
marked them up with tippex before I started. I was intending to do the whole thing without having to lock the cams. When it wouldn't start the first time decided to get some locks & do it the fiat way. As a result the cam pulleys have moved in relation to the cams so all the marks no longer mean anything.

Thankfully me dad is going to lend me his dial guage so I'll be able to properly determine tdc later today (hopefully).
 
So you set TDC through the plug hole with a dowel, set the cams where they were with tippex marking fitted the new belt (did it slot on nicely with the cams in position?) and the car would not idle?
If thats true then sensor damage while you were working on it seems likely. Getting it into limp home with the mass sensor off and away to a diagnostic expert may be your best way forward.
The dial gauge will help since the piston stops then goes down TDC is hard to find (it doesnt move far on a modern short stroke engine anyway). If the dial gauge does not do it then you also have to consider the position of the cams. Not sure if this is even in the public domain, although you can make an estimate of about 260 degrees of overlap in a mild street engine.
 
So you set TDC through the plug hole with a dowel, set the cams where they were with tippex marking fitted the new belt (did it slot on nicely with the cams in position?) and the car would not idle?
If thats true then sensor damage while you were working on it seems likely. Getting it into limp home with the mass sensor off and away to a diagnostic expert may be your best way forward.
The dial gauge will help since as the piston stops then goes down TDC is hard to find (it doesnt move far on a modern short stroke engine anyway). If the dial gauge does not do it then you also have to consider the position of the cams. Not sure if this is even in the public domain, although you can make an estimate of about 260 degrees of overlap in a mild street engine.
 
belt.jpg


Yip, that's right. The belt went on fine and everything just slotted nicely back into place.

We've just finished setting it all up again using the DTI and the locks. Guess what - it won't run. And now it won't even attempt to start again as the battery's flat!

It's possible that when i was cleaning the pulleys with brake degreaser it's damaged the cam position sensor. I also had to remove the resonator in order to get the engine shoved over to the nearside so that the new tensioner could be fitted. This may have badgered the air mass meter. Driving without an air filter for 10 miles is usually enough to kill them, - they're dead fragile.

Think I might try the RAC. You never know, they may come out with the right module to connect up to a FIAT diagnostic socket.
 
Charged it up today & tried it at lunchtime. It starts, but again, only with the air mass meter disconnected.

Went to Gainmanor at silverlink to follow up on another hunch I had. The destructions that came with the locks says to lock Inelt #2 and exhaust #3. Where fiat say lock Inlet #3 and exhaust on #2. Their mechanic was very helpful & went to get his locks to compare them with the ones I've got. They're identical. However, he did say that he remembered doing a coupe a long time ago and having exactly the same trouble. he couldn't quite remember how he got it working in the end but did say that there was an issue with the fiat instructions.

Does anyone have any other instructions on which cams to lock and at what position?

Top marks to Gainmanor, it's rare to find a fiat garage so forthcoming, me dad even said that he'd go back with me mum for her new punto.
 
Finally got it working! :D

Went to Benfield in Newcastle and spoke to one of their mechanics.

Apparently the original FIAT manual is incorrect and tells you to lock the wrong lobes. Some lock manufacturers used this info to produce their instructions - like mine. The second edition manual (the one I have) has this corrected. But me having two opposing sets of instructions didn't boost confidence in what we were doing much.

He also said to totally ignore the alignment marks on the pulleys and belt. The correct procedure is as follows

  1. Set crank at ~=TDC for #1 using timing mark on oil pump housing and gear
  2. Remove cam caps for #3 inlet and #2 exhaust and rest locks in place. Do not bolt down.
  3. Remove old belt
  4. Loosen both cam pulleys
  5. Lock cams with bolts (use M7 x 60mm bolts and a stack of washers as the ones from the caps are too short)
  6. Use dial gauge with long probe to find true TDC (we used a thin plastic tube)
  7. Fit new belt and set tensioner to max. Check dial gauge hasn't moved.
  8. Tighten cam pulleys
  9. Remove locks and rotate engine 2 complete revolutions.
  10. Lower tensioner setting to the mark on the tensioner back plate.
  11. Rotate twice again and check nothing's slipped.

He also said to check the idle control valve as these are known to stick if you disturb the engine. So off we went trying to find this. Which we couldn't as the electronic throttled engine doesn't have one. What we did find though was that the hose from the AMM to the throttle body had slipped off the bottom of the throttle as the clip hadn't been done up at a previous service! :bang:

Refitted everything, including the offending hose and fired up - worked first time. :D

Thanks to everyone for you help. It was very much appreciated. :worship:
 
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