sierra motor won't rev

[Zachius]

Having issues with my sierra atm.

I was driving along, when i suddenly lost a lot of power and a noise started coming from the motor.

When standing still and revving in neutral it seems mostly okay. It has momentary hesitation when you lift your foot off and put if down.

When driving it only revs to around 4k and will not rev any higher.

I have tried the hand over the carby trick. Did not make any difference. The accelerator pump appears to be working okay, you can see the fuel been squirted in when you crack open the throttle.

How much should the secondary throttle butterfly open when giving it some revs in neutral? ATM, it just starts to crack open, so I am assuming that is working correctly.

I am thinking it is more than likely a carby issue. Something to do with fuel not getting to the secondary jet. I am considering taking the carby off and pulling it apart and giving it a clean.

Any advice is greatly appreciated.

[zookimal]

Had similar issues once and it was a blocked carby jet.

Exactly the same symptoms.

[Zachius]

Thanks. Now I have to find the time to clean out the carby... amongst work and uni atm I don't have too much :-(

[JrZook]

Having issues with my sierra atm.

I was driving along, when i suddenly lost a lot of power and a noise started coming from the motor.

When standing still and revving in neutral it seems mostly okay. It has momentary hesitation when you lift your foot off and put if down.

When driving it only revs to around 4k and will not rev any higher.

I have tried the hand over the carby trick. Did not make any difference. The accelerator pump appears to be working okay, you can see the fuel been squirted in when you crack open the throttle.

How much should the secondary throttle butterfly open when giving it some revs in neutral? ATM, it just starts to crack open, so I am assuming that is working correctly.

I am thinking it is more than likely a carby issue. Something to do with fuel not getting to the secondary jet. I am considering taking the carby off and pulling it apart and giving it a clean.

Any advice is greatly appreciated.

Noise started comin from the engine? Care to explain. If you were driving along and all of a sudden u lost power the cam belt may have slipped a few teeth.
Secondaries in a std zuk carb are vacuum operated, hence they will only open up under load. Sounds like its not the problem. Zuk engine will still rev past 4k even with only the primary throat.

Cheers Dan

[Tim D]

Have you checked the exhaust ?
Might have blown the gasket ?
Might be cracked rusty pipe ?

Head gasket maybe ?

[Zachius]

thanks for the replys.

It does not have any symptoms of something mechanically wrong in the engine, it still runs smoothish as and the exhaust has recently been fixed. No head gasket symptoms either. No bubbles in the water or oil residue or anything of the sort.

I swapped the carby over to a spare one I had, pretty sure the cut off solenoid is stuffed on mine anyway. That did not make too much difference.

I think I have tracked the problem down to the ignition coil. When i pulled the lead that runs from the coil to distributer there was a lot of corrosion and white powder there. I cleaned up the connector as much as possible and connected the coil back up, it seemed to be slightly better when I went on a short drive but seemed to get worse quickly and was pinging very erratically.

I can hear the cooling liquid sloshing around in the coil when I shake it which along with the behavior of the motor would seem to indicate the coil is probably stuffed. I should be getting a new/second hand one over the next couple of days, fingers crossed that it resolves the problem.

[Tim D]

New coil sounds good, while your at it
plugs, leads, rotor cap

if you haven't done them already.

[suzimad]

blocked catalytic converter

[Zachius]

I don't think there is much left of the cat converter

[lay80n]

Vacum advance failure/fault?

Layto....

[mrw82]

have you got it sorted?

if not than this might help:

I had a similar thing in mine, wouldnt rev past 4500 and when it was up there it was being a rice bubble (you know, snap, crackle, pop)

ended up being bad fuel.
the best way to rule it out is disconnect the fuel line from the pump (tank line) run the engine until it stops. (my zook ran for about a minute just on the fuel that was left in the pump and carby, really didn't expect it to go that long)
then hook up a length of hose into a jerry can of fresh fuel, crank it over and see if it made any difference.
if it does fix the problem then drain your tank, change your filter and blow the lines out to get rid of all the bad fuel.


cheers, Mark.

[Zachius]

nah haven't got it sorted yet... I bought new spark plug leads and changed the coil, no success so far.

Is it true that whitish sparkplugs indicate the correct fuel/air mixture, thus meaning it is almost certainly a ignition issue rather than a fuel/air issue?

Hopefully, I will replacing the distributer cap tomorrow as there are some very faint lines running between the contacts and the contacts themselves are worn somewhat. I might pick up a second hand coil as well, as the replacement was not off a suzuki and am not 100% confident of its condition.

I did consider the possibility of bad fuel. I use shell E10, and bought the fuel from the same fuel station as I normally do. When i started having these problems the fuel tank was near empty, so I went and filled it up the other day. I would have thought that filling it up would have changed something if it was bad fuel. If the distributer cap does not solve it I may be doing this just to rule it out, as it is somewhat easier to rule out than the remaining possibilities

Considered the possibility of a vacuum advance problem but the symptoms don't really match. It pretty much pings randomly throughout the rev range. When I went for a drive after changing the coil it was pinging when accelerating out of an intersection at <3k RPM, plus with the backfiring out of the carby.

New symptom when I changed the coil, it now seems to be backfiring out the carby when held at 4k RPM in neutral. This leaves 4 possibilities as far as I can see, coil, distributer cap, spark plug leads and stuffed valve seal. I have changed the leads and coil so I am hoping that it is the distributer cap

[JrZook]

Is it true that whitish sparkplugs indicate the correct fuel/air mixture, thus meaning it is almost certainly a ignition issue rather than a fuel/air issue?



I did consider the possibility of bad fuel. I use shell E10, and bought the fuel from the same fuel station as I normally do. When i started having these problems the fuel tank was near empty, so I went and filled it up the other day. I would have thought that filling it up would have changed something if it was bad fuel.

Considered the possibility of a vacuum advance problem but the symptoms don't really match. It pretty much pings randomly throughout the rev range. When I went for a drive after changing the coil it was pinging when accelerating out of an intersection at <3k RPM, plus with the backfiring out of the carby.

New symptom when I changed the coil, it now seems to be backfiring out the carby when held at 4k RPM in neutral. This leaves 4 possibilities as far as I can see, coil, distributer cap, spark plug leads and stuffed valve seal. I have changed the leads and coil so I am hoping that it is the distributer cap

All of these symptoms could point to a very lean running engine. White plugs, backfiring out of the carb, pinging under load. Also i wouldn't be to keen in the E10 through the carb, dont know the effect of the ethanol on the gaskets and other parts such as the fuel pump diaphragm. Have you tried normal fuel yet? You may be having fueling problems blocked carb, dying fuel pump etc.

But then its interesting about the symptom when you changed the coil. Have you put a timing light on it yet?

Cheers Dan

[mrw82]

If your using E10 then definately do as I described in regards to it being a fuel issue and make sure you test it with regular ULP.

[built4thrashing]

iv'e tried the E10 fuel and suzuki's dont like it. disturbs all the ulp sludge in the fuel system and plays havoc with filters and jets. Drain whats left of it and run a tank of premium . should clear up ya probl;em then go back to using normal ULP.

not worth the hassle just to save a few cents on ya fuel cost with the E10 crap

[Zachius]

i have been running it on E10 for over a year, I am very doubtful that it is a fuel issue. As i said the whole carby has been replaced with a spare one I have. I will consider fuel issues again after I have ruled out the ignition system.

It seems to run better on E10 in general, but like you say I am not entirely sure of the effect it has on rubber fuel lines, fuel pump diaphragm and gaskets. The filter was very clean when i checked it and I replaced it to make sure.

Something else that I forgot to mention is that when I had a look at the distributer cap there seems to be two very faint lines connecting three of the contacts. At this stage I am pretty sure that it is the distributer cap causing the problem.

I have not put a timing light on it as I do not have easy access to one.

[Santos]

i've been running e10 for almost 3 years now, when i finally do tear the engine down i am really curious to see what the insides look like (55000kms so far )

[Zachius]

Replaced the distributer cap with no effect.

So after asking some advice from a local friendly mechanic I proceeded to take off the timing belt cover. When I peered down past the cover after having removed a few bolts, I could see the tensioner spring laying at the bottom of the case. Not a good sign!!!

After finally removing the timing belt cover completely it would seem that the timing belt has jumped two teeth. As far as I can work out this is a result of the end of the tensioner spring breaking off and the tensioner spring falling down between the belt and gear. The crankshaft timing belt gear has a few light marks on it as well.

I am probably lucky it did not jump a few more teeth and send the pistons and valves crashing into each other

So i have a couple of questions, what is the actual purpose of the tensioner spring? I really do not understand the purpose of it.

Secondly when I look at my timing belt gear on my camshaft there is two marks on it. One marked 80C and another 60A, one also has a second raised dot marking it. Any ideas on the purpose of these two marks and which one is the correct one to do the timing off?

Should I replace the timing belt? It does not appear to be damaged. Do I need to replace the tensioner spring?

[Zachius]

Here is a photo of the camshaft marks I am talking about.

[JrZook]

Noise started comin from the engine? Care to explain. If you were driving along and all of a sudden u lost power the cam belt may have slipped a few teeth.
Secondaries in a std zuk carb are vacuum operated, hence they will only open up under load. Sounds like its not the problem. Zuk engine will still rev past 4k even with only the primary throat.

Cheers Dan

Bingo! Thats what the noise was you heard from the engine. Was blowing back out of the carb because the valve timing was off!
Exactly the same thing happened to mine with that tensioner spring. I would check over the belt carefully and possibly replace it if its damaged. As for the spring I left that out and tensioned the belt manually. Didn't want that to happen again. It is there to provide the 'tension' on the belt before you nip up the adjustment bolt.

Dan

Dan [/b]

[Santos]

is this the original motor? if so what year is it?

[NIK]

Was reading through and going to say timing, mine jumped a few teeth as well.
Cant say I noticed the 2 timing marks on my cam pulley, does it mention it in the manual? I think mine lines up with a line not a dot.
There was a write up awhile back on ethanol fuel and I think it was desided it runs crap because it cleans all the lines and tank etc with initially block the filters jets etc but once thats sorted its all good and actually runs a bit cooler. I could be wrong though.
Nik

[Zachius]

yeh it is the original motor, car was built in 95.

I will (hopefully) be fixing it tomorrow after I buy a new timing belt. Asking a friend about the timing mark and will be doing it off valve position. The vavles on piston 4 should be rocking between closing exhaust and opening inlet when all the marks line up. This makes sense to me so I will double check it against the marks when i find out which mark makes sense.

I have also noticed that my passenger side engine mount appears to be broken. Where would be the best place to get a new one?

There is lines on the edge of the camshaft timing gear if you look at the picture

[Zachius]

All back together now and back on the road

Had to replace the rocker cover cork gasket as I think I originally put it on with the gasket in the wrong place, it leaked so then I tightened the bolts (stupid idea I know) and that made it even worse and pretty much destroyed the gasket. The gasket only cost $16 so it did not cost me two much.

The tensioner spring just seems like a silly design to me. It basically has no functional purpose and can cause issues like this