[rob_macca67]

HI all...

Just after some advice on the following;

No.4 cyclinder seems to have problem.... The engine seems to have a miss and when I remove No.4 lead, there is no change in engine idle but with the other cylinders there is a change in idle when lead is removed. I've swapped plugs with no changes & I've checked for a spark on No.4 lead... aok.
I've just done a compression test with the following readings:
(Dry Test)
No.1 - 120
No.2 - 125
No.3 - 125
No.4 - 125

(Wet Test)
No.1 - 125
No.2 - 130
No.3 - 130
No.4 - 130

The engine has a engine knocking noise upon startup (seems to be coming more from top of engine) & as the motor warms up the engine knock slowly seems to dissappear....
The motor does blow smoke (blue I think...) when u rev it and is fumey...

Any ideas from the more experienced people out there......

cheers....

rob

[unique_seek]

so your saying its only running 3 cyl?tested leads?checked dizzy cap?

[rob_macca67]

Yes.. it appears to be running on 3 cylinders.....

I've got spark at No.4 plug but I haven't checked the lead as I thought it would be ok if there is spark already there.... Is this wrong??

what should I be looking for re: dizzy cap??

rob

[unique_seek]

how did you test the spark?check the leads with a multimeter,ohms and measure the resistance,if its over about 10-15 than it may need replacing.try swoping 2 leads around(swop on the dizzy and on the plug)

If you have spark,it may be ok,but under compresion spark can change.when you tried switching the plugs did it change at all?

[unique_seek]

take the cap off and check for carbon build up on the 4 point where the leads go on(inside the cap) and also check the rotor button.

[royce]

"checking spark" you want to be able to jump about 4" of free air to be enough for a plug, try swapping leads and look for cross shorting

[rob_macca67]

royce wrote:

"checking spark" you want to be able to jump about 4" of free air to be enough for a plug, try swapping leads and look for cross shorting

4" (100mm) of spark seems a long way.... would that be the same on any petrol car??

rob

[zookster666]

Swap 2 leads and see if the miss changes to that cylinder that no4 lead went onto, simplest way to check the lead

jesse

[royce]

rob_macca67 wrote:

royce wrote:

"checking spark" you want to be able to jump about 4" of free air to be enough for a plug, try swapping leads and look for cross shorting

4" (100mm) of spark seems a long way.... would that be the same on any petrol car??

rob

yeah pretty much, the cylinder is under pressure and has fuel to compete with too, you ned a fair wack of volts to sort that stuff out

[Damo]

rob_macca67 wrote:

HI all...

Just after some advice on the following;

No.4 cyclinder seems to have problem.... The engine seems to have a miss and when I remove No.4 lead, there is no change in engine idle but with the other cylinders there is a change in idle when lead is removed. I've swapped plugs with no changes & I've checked for a spark on No.4 lead... aok.
I've just done a compression test with the following readings:
(Dry Test)
No.1 - 120
No.2 - 125
No.3 - 125
No.4 - 125

(Wet Test)
No.1 - 125
No.2 - 130
No.3 - 130
No.4 - 130

The engine has a engine knocking noise upon startup (seems to be coming more from top of engine) & as the motor warms up the engine knock slowly seems to dissappear....
The motor does blow smoke (blue I think...) when u rev it and is fumey...

Any ideas from the more experienced people out there......

cheers....

rob

Did you do the compression test correctly?

Those readings are very low. Standard compression should be 199 psi, with a service limit of 170 psi. Are the valves adjusted properly? Maybe they are a bit tight.

[Built4thrashing]

check ya plugs to see what color the electrode is after a drive. this will help determine whats stopping the spark. If its black and covered in sludge then ya have an oil fouling issue from either rings or stem seals.

[rob_macca67]

Damo wrote:

Did you do the compression test correctly?

Those readings are very low. Standard compression should be 199 psi, with a service limit of 170 psi. Are the valves adjusted properly? Maybe they are a bit tight.

Damo... I believe so..... I removed all plugs & inserted the tester into the sparkplug slot & turned the key over for the motor to wind over 5/6 times... is that correct??

I just measured the resistance of the leads as follows:
No.1 - 3.15k ohms or 3150ohms (longest lead)
No.2 - 3.11k ohms or 3110ohms (2nd longest lead)
No.3 - 2.62k ohms or 2620ohms (3rd longest lead)
No.4 - 2.72k ohms or 2720ohms (4th longest lead)
Coil lead - 1.53k ohms or 1530ohms (shortest lead)

I assume that the resistance should get less the shorter the lead gets??

Are these readings about right??


rob

[Damo]

rob_macca67 wrote:

Damo... I believe so..... I removed all plugs & inserted the tester into the sparkplug slot & turned the key over for the motor to wind over 5/6 times... is that correct??

Hold the throttle wide open as you do it too

rob_macca67 wrote:

I just measured the resistance of the leads as follows:
No.1 - 3.15k ohms or 3150ohms (longest lead)
No.2 - 3.11k ohms or 3110ohms (2nd longest lead)
No.3 - 2.62k ohms or 2620ohms (3rd longest lead)
No.4 - 2.72k ohms or 2720ohms (4th longest lead)
Coil lead - 1.53k ohms or 1530ohms (shortest lead)

I assume that the resistance should get less the shorter the lead gets??

Are these readings about right??

Yes there should be less resistance in the shorter leads. I'm not sure what the resistances should be that that would appear to be OK. If it was a problem with a lead then that one should be vastly different to the rest, and from those figures that does not appear to be the case.

[Rockhopper]

Anymore than about 12k ohm for a lead and it's time to bin, so those readings look ok. Those compression readings are low, but are consistant, so you may want to check you valve clearances. When you pull number 4 plug out what does it look like?? Is it wet/dry/black/gunked up? Swap the plug with another cylinder and see if that makes the other cylinder miss or if the miss is still in number 4. Check for a vacuum leaks as well, particularly around #4 cylinder. I think the brake booster probably feeds off #4, so check that and also the vacuum hose to the manifold from the booster.
Hope this is of some help. Keep us posted.

Elio

[Scrawny]

From memory resistance should be 1k ohm per 100mm.... someone correct if I'm wrong.

[rob_macca67]

Rockhopper wrote:

Anymore than about 12k ohm for a lead and it's time to bin, so those readings look ok. Those compression readings are low, but are consistant, so you may want to check you valve clearances. When you pull number 4 plug out what does it look like?? Is it wet/dry/black/gunked up? Swap the plug with another cylinder and see if that makes the other cylinder miss or if the miss is still in number 4. Check for a vacuum leaks as well, particularly around #4 cylinder. I think the brake booster probably feeds off #4, so check that and also the vacuum hose to the manifold from the booster.
Hope this is of some help. Keep us posted.

Elio

Elio....No.4 Plug does look wet & black....I have swapped plugs and leads & it doesn't really make any difference....

Vacuum leaks is something I'll have to check but I might look at checking / adjusting the valves first.....

Thanks for your help, cheers...
rob

[rob_macca67]

ScrawnC wrote:

From memory resistance should be 1k ohm per 100mm.... someone correct if I'm wrong.

Scrawny.... Is this standard across all leads and I gather that as a lead is getting to the "stuffed" stage, that the resistance increases.... is that correct??

rob

[Scrawny]

yes and yes.

[rob_macca67]

Damo wrote:

rob_macca67 wrote:

Damo... I believe so..... I removed all plugs & inserted the tester into the sparkplug slot & turned the key over for the motor to wind over 5/6 times... is that correct??

Hold the throttle wide open as you do it too
quote]

Damo... I may have done it incorrectly... I was told to remove ALL 4 Plugs, then insert the tester in one of the plug positions & then crank the motor over 5 or more times. Then take the reading then.... Is this correct??

You lost me a bit when u said to hold the throttle wide open as I'm not sure what difference that would make....?

rob

[rob_macca67]

zookster666 wrote:

Swap 2 leads and see if the miss changes to that cylinder that no4 lead went onto, simplest way to check the lead

jesse

Done this.... no difference.....

[Scrawny]

Holding the throttle open allows unrestricted airflow into the chambers. If the throttle is left closed then there is vacuum created in the intake. Sometimes the throttle doesn't affect the reading, sometimes it can give you lower readings.

[rob_macca67]

Built4thrashing wrote:

check ya plugs to see what color the electrode is after a drive. this will help determine whats stopping the spark. If its black and covered in sludge then ya have an oil fouling issue from either rings or stem seals.

The No.4 Plug is wet & black

[rob_macca67]

ScrawnC wrote:

Holding the throttle open allows unrestricted airflow into the chambers. If the throttle is left closed then there is vacuum created in the intake. Sometimes the throttle doesn't affect the reading, sometimes it can give you lower readings.

Thanks Vaughn... I wasn't aware of this.... I'll redo the Compression Test again to see if there is any difference in readings....

rob

[Scrawny]

What did you do different for the 'wet' test? Did you use oil?

[rob_macca67]

ScrawnC wrote:

What did you do different for the 'wet' test? Did you use oil?

Yeah... That's what I was told to use..... Is that OK?

[Scrawny]

Yeah, just curious that's all.

[rob_macca67]

ScrawnC wrote:

Holding the throttle open allows unrestricted airflow into the chambers. If the throttle is left closed then there is vacuum created in the intake. Sometimes the throttle doesn't affect the reading, sometimes it can give you lower readings.

Vaughn.... I did the test again with the throttle open.... very little difference to the initial readings.....

rob

[blingdup]

Have you checked strength of spark as Royce said.
Ive never seen a spark jump 100mm, but if it cant jump 25-30mm there is a restriction somewhere. If youve swapped plugs and leads over without any change, have a good look at the dissy cap, particularly around no4, for arching or dirty contacts.

[Brett]

your plug might of just died(cracked tip or in the white bit) how old are they? i'd replace them if you don't know how old they are.

your leads look ok, compression is even so its spark and your getting that to the plug but not into the cyclinder that leaves the plug.

[royce]

keep cranking till the reading doesnt get any higher, not 5 turns