Where to start if your CF is misbehaving and you're not sure where the problem may be.

Missfire and lack of power when acceleration.

Post by Bennybedford » Subscribing Member » Sat Jul 07, 2018 1:53 am
Joined: Thu Aug 24, 2017 11:59 pm
Posts: 17
Hey,

I changed the cambelt for the first time a week ago, I marked it up and got it back on the same position. I doubled checked with the "TDC pin" and with a straw from the v to the circle like in your picture. The TDC pin was in the "middle mark" and not on the 9 degree sign on the plastic cover, is that correct?
The rotor is pointing on the first cylinder and the pistong was on the top. So far so good.
The idle yet is perfect and when I drove away to test it, there was no problem. But when I came out on the road, pressed down the pedal more quickly I lost all power, missfired, and felt like it almost died. When releasing the pedal it goes all normal and I can still get up in speed by gently press the pedal.

When idling and press down the pedal full it hesitates and missfire, but then I give it choke at the same time its fine, it will not hesitate while giving full gas at all. This make me feel like it has something to do with the fuel more than the cambelt, but what do you think? Is there a chance that I have done something wrong with the cambelt or is it just a coincidence that another problem happens to be right now?

Things i checked.
-I found water under the ignition distributor cap (Had some fighting when refilling the radiator..) i have dried it and checked the cables and condensator, looks good but still a little bit worried that there is water under it that you cant see or it had some short circuit?
-Checked vacuum hoses, air cleaner and the operation to the inlet house opens and remain open while sucking on the vacuum hose.
- I have cleaned the filter in fuel pump.
-Changed sparkplugs, the old was really sooty wich are strange if there is not enough fuel, right?


Alot of quesitons and not the best english, but i would be really grateful if you had some input what to look for..
Best regards

Re: Missfire and lack of power when acceleration.

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Post by Phil Bradshaw » Club admin » Sat Jul 07, 2018 6:22 am
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3543
If the engine runs fine when cold but starts to misfire as it warms up then check distributor again for condensation inside the cap.

Fix is to leave the cap off to allow any water lodged in the bottom of the distributor to evaporate while the engine still is warm.

Might take more than one drying session to completely clear the problem. Make sure that the cap is clean before refitting it; a light spray of WD40 inside the cap can help too.

Also check ignition timing at idling speed with a timing light, vacuum disconnected from distributor and hose plugged.

If distributor is clear of condensation and timing is correct but power loss on acceleration remains then is the power loss (a) like switching off the ignition or (b) more like fading away due to lack of fuel?

If (a) then don't encourage the misfire in case an electrical fault clears when there is unburnt fuel lodged in the silencer which then can burst if hot exhaust gases ignite the unburnt fuel.
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  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Missfire and lack of power when acceleration.

Post by Bennybedford » Subscribing Member » Sat Jul 07, 2018 2:00 pm
Joined: Thu Aug 24, 2017 11:59 pm
Posts: 17
Now I have dryed the distributor by warming up and taking of the cap, also ordered a new condenser, looked really bad.
I also found that the second cable next to the condenser, maybe earth cable? had some scratches on the cable, temporarly fixed it to see if it helps.

So I wait for the condenser that will come on tuesday to check.

Here is also a video of how it sounds. As you can see, if I choke or gently press down the pedal its no problem to get in high rpm, but directly pushing down it will fail.



Image

Image

https://youtu.be/grvdv7yldnc

https://imgur.com/cOMmYvB

https://imgur.com/i90lEg7

Re: Missfire and lack of power when acceleration.

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Post by Phil Bradshaw » Club admin » Sat Jul 07, 2018 3:08 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3543
Faulty condenser can cause misfiring when the distributor is hot. Check contact breaker faces for blackening to confirm faulty condenser; faces otherwise should be a matt grey colour where contact is made. However, fitting a new condenser usually is the best way of checking.

Black wire in distributor is the earth lead for the contact breaker base plate. If the wire separates when gently pulled then this is the most likely problem because it can separate when the base plate moves with vacuum advance, when the ignition system will stop working until the wire break joins up again. Same applies to the coil LT lead (white+black) between the knot and terminal if the insulation is damaged but this is not as common as broken earth leads.

Distributor has to be removed for dismantling to replace the base plate earth wire. Replacement wire should be as flexible as possible to allow free movement of the base plate: do not use ordinary vehicle harness cable. Non-insulated fork terminals for M3 screws should be crimped on rather than soldered.

Lubricate the mechanical advance mechanism contact points! (Spring posts and weights including under each advance weight.)

Also check for wear of the contact breaker plastic heel causing points gap to close up. Distributor cam should be lightly smeared with lithium (wheel bearing) grease so that a fillet approximately 1.5mm thick builds up on the plastic heel when the distributor shaft rotates.

Howto for Delco D300 might be useful. :thumb:

Also, if the small diameter pipe that goes beyond the rear of the engine is for the vacuum modulator on automatic transmission then check for leakage at the intake manifold connection and at the modulator (which looks like a distributor vacuum unit).
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  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Missfire and lack of power when acceleration.

Post by Bennybedford » Subscribing Member » Tue Jul 10, 2018 3:10 pm
Joined: Thu Aug 24, 2017 11:59 pm
Posts: 17
Hi,

I have now changed the condenser and new earth cable, TDC and put it back in with the rotor pointing to the first cylinder cable, but now it dont even start...
I tried to spin the distributor a half but then i get missfires, so I assume the other is the correct way.. I also tried to spin the bottom of the distributor in different way but not any succeed.

I cant hear any bad sounds, it cranks really easy.

The usual question, what can I have done wrong?

Re: Missfire and lack of power when acceleration.

Post by Bennybedford » Subscribing Member » Tue Jul 10, 2018 3:29 pm
Joined: Thu Aug 24, 2017 11:59 pm
Posts: 17
I havent changed the position on anything, but is there any mark on the distributor body that i can look for? Cant see any.

Re: Missfire and lack of power when acceleration.

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Post by Phil Bradshaw » Club admin » Tue Jul 10, 2018 4:19 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3543
Check for sparking from the coil HT lead.

If sparks are thin or erratic then try the old condenser in case the new condenser is faulty.

If no sparks then check connections inside distributor (e.g. wire/s to contact breaker shorting to ground).

If sparks are good and steady then check ignition timing: contact breaker points should just start to open at 9º before TDC.

At 9º before TDC the distributor securing bolts should be roughly central in their slots with contact breaker gap at 0.5mm (0.020 inch).
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  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Missfire and lack of power when acceleration.

Post by Bennybedford » Subscribing Member » Tue Jul 10, 2018 9:10 pm
Joined: Thu Aug 24, 2017 11:59 pm
Posts: 17
Hey Phil,

I have checked and there is good sparks, breaker points on 0.5mm and the contact breaker looks good.
Changed back to the old condensator with no result, all cables looks good..

I get sparks and it backfires sometimes when i give gas, tried to set the ignition in different positions but with no result.

I took of the fuel hose from the carburettor and it sprayed out petrol, so the pump is ok..

Re: Missfire and lack of power when acceleration.

Post by Bennybedford » Subscribing Member » Tue Jul 10, 2018 9:14 pm
Joined: Thu Aug 24, 2017 11:59 pm
Posts: 17

Re: Missfire and lack of power when acceleration.

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Post by Phil Bradshaw » Club admin » Tue Jul 10, 2018 10:55 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3543
Video clip: spit back through the carburettor/air intake indicates ignition system working but distributor in the wrong position.

When setting TDC with the cam belt cover fitted there are two possible positions for TDC - No. 1 or No. 4 cylinder at the start of its power stroke just after contact breaker points open.

Quick check: swap plug leads 1 for 4, 2 for 3. If engine tries to run then distributor needs removing to turn rotor and shaft 180º.

Two ways for checking to be sure.

1. Remove cam belt cover to re-align cam belt timing marks at TDC, when No. 1 cylinder is at the start of its power stroke and distributor rotor should point towards camshaft (No. 1 plug lead).

or

2. Remove camshaft cover then watch for valve overlap on No. 4 cylinder as crankshaft is rotated clockwise to TDC.

Overlap at TDC is when exhaust valve is closing and inlet valve is starting to open (end of exhaust stroke, start of intake stroke).

In this position No 1 cylinder is at the start of its power stroke with both valves fully closed and distributor rotor should point towards camshaft.
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  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

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