4kc breaking up

[Braydenj]

Hey guys I am having trouble with my 4K in my ke70 and need advice or help on things to check or if anyone has had similar problems.

 

today I was covering a bit of ks and had done about 170ish ks in several separate trips had been fine all day when all of a sudden down the freway it started breaking up

I have isolated the problem it will only do it in 4th gear when holding a constant speed. under acceleration it is normal when I let of the pedal and deceleration it is also normal no breakup ect. (On a side note it also stalls out when trying to down shift from 4th to any gear as soon as the clutch is pushed in idle just drops to nothing and stalls out)

So the problem kind of feels like a bunch of mini fule cuts happening over and over constantly when cruising as stated above. Keep in mind it was doing this before and breaking up every now and then but nothing concernable in the same conditions as above. (This would happen like once or twice every 2-3 km then be fine where as now it is basically constant)

it is like it is having trouble holding the fule at a certain level while cruising but only in 4th gear

my initial idea was a fule like split or something so it was sucking in air however under heavy acceleration it is fine and does not do it. Maybe a spark plug but then why is it driving fine in every other gear and any other time. Is my flywheel or clutch catching causing the jumpy feeling? Never heard of this issue before but who knows? Is there any fule solenoids or fuses ect I could check?

any ideas help as I’m a bit lost atm cheers fellas

[altezzaclub]

A four-speed right? So 4th is where the motor works hardest and things break down easiest. When you're doing a cruising speed and it happens, push the clutch down and turn it off, then coast to the side of the road and take out the plugs.

See if one spark plug is worse than the others, and start chasing the electrics for that plug- swap the plugs around for a while, do another plug cut and see which cylinder is bad. Same cylinder or same plug?  Swap a lead if you can and try it, replace the distributor cap.

If the plugs look the same, the problem is more general-

On cruise the advance goes high, so it could be in the weights & springs below the distributor base, the points, the condensor or the coil. Check the rotor and distributor cap too, look at the leads one wet night with the motor running and see if they are leaking high voltage.

The carb runs on the main jets at cruise, adds the pump jet to accelerate, so maybe it leans out on the main.  It will use less fuel when cruising so enough fuel gets delivered for cruise if it accelerates in 4th, and that rules out fuel filter and pump as the cause.

"as soon as the clutch is pushed in idle just drops to nothing and stalls out"

Cruise and idle activate the PCV valve, so clean that out with petrol and make sure it seals when you suck in one direction, and flows in the other. If its not sealing it will lean the motor out at cruise and idle.

You might have the fuel cut-off solenoid on the side of the carb that cuts fuel when you turn the motor off, but it would be most unlikely that it is cutting in and out at cruise.

Let us know how you go-

Edited October 24, 2024 by altezzaclub

[Banjo]

Hi Brayden,

                    Read your queries, with interest; & Altezzaclub's response, which as always; is very thorough.  There was line in His advice that jumped out at me.

Quote

You might have the fuel cut-off solenoid on the side of the carb that cuts fuel when you turn the motor off, but it would be most unlikely that it is cutting in and out at cruise.

Several years ago, I took my KE30, with a 4K-U engine, down the inland New England highway, from Brisbane - Sydney.  Somewhere up near Guyra, the car started to develop, very similar issues, as You describe.  I pulled up in a public car park, right across from a motoring store, so if I needed anything, I didn't carry in my boot, then I had access to it. 

I did all the usual things like clean the bowl & jets in the carby, & unhooked the fuel line at the carby, & turned the engine over, to ensure I had fuel delivery. All good !

I took it for a run, & for 20 minutes; & it was running pretty good. I was just about to "pat myself on the back", when it occurred again, well away from any town.

I pulled up in a little park, near a bridge, & lifted the hood/bonnet again.  

Yes it was the fuel cut-off solenoid, which is energized, whilst ever, the ignition switch is on.  I disconnected the wire from the carby assembly, that was just a push-on connection.  I then hooked my trouble lamp up to this wire from the ignition, & an earth; then turned on the ignition. The trouble lamped lit, but when I started tracing the wire back from the carby, & started wriggling the wires, the test lamp flickered.  Found the crook connection; corrected same, & I was on my way to Sydney, without any further issues.  However, the symptoms whilst driving, were similar to what You described in your post. 

I hope it is the same fault in your car, because the intermittent wire connection, to the fuel solenoid, is a very easy, & clean fix. 

P.S.  However, if You come back, & advise your engine does not have a fuel line cut-out, on your particular carby; then We are unfortunately; back to square one again !

Let's know how You go.

Cheers Banjo

 

Edited October 24, 2024 by Banjo