5K Cutting Out At Higher Revs

[flamingheads]

I've finally got my 5K running, done the timing, tuned it and it seems to be running totally fine but at 2 points in the revs it totally stops getting power so I get jerked forward in my seat. If I back off a bit I can keep accelleration I can rev higher then it does it again and I have to back off more.

It's got a weber, I don't know what the specs are but the previous owner had it on the motor and said he rejetted it and everything and it runs fine at anything but hard accelleration.

 

Also the sump is only just touching the crossmember, which makes the whole car vibrate and rattle. Is this normal? Should I try putting the 4K sump on instead?

[Trev]

Point's ignition?

 

Make sure the gap is set correctly, the wrong gap can lead to ignition break down at high rpm.

 

The FAQ states to use the 4k sump if the sump has clearance issues, the one in the ke70 van I had must of been a 4k sump as it had plenty of clearance.

 

http://www.rollaclub.com/faq/index.php?title=Sump

[altezzaclub]

Do you think it is where the second choke opens and it suddenly leans out??

 

A dyno run would soon sort it, fuel or electrical.

[Taz_Rx]

4k and 5k sumps are the same.

 

Are you running a stock fuel pump? Could be that you're draining your float bowl and and thats why your pulling up.

[flamingheads]

It's got electronic ignition so no points.

 

I can put my foot down and it's fine up to a certain revs, then suddenly it cuts out and I have to back off. Maybe when I back off it closes the second choke then it gets the right mixture of fuel air again?

 

The guy I bought the engine off was running the mechanical fuel pump so I thought it should have been fine. I added a fuel return line he had blocked off so maybe thats affecting it somehow?

 

A dyno run would be nice but I'm very low on cash at the moment so it's not really an option for me.

 

Thanks for the ideas so far.

 

Some more things I thought could be wrong: What should change at high revs? Should it get more fuel or is there a vacume advance with electronic ignition that should advance the timing or something? Should there be a second jet of fuel when the throttle is opened more I could look at by taking off the air filter?

[Trev]

4k and 5k sumps are the same.

 

Are you running a stock fuel pump? Could be that you're draining your float bowl and and thats why your pulling up.

 

Yeah I thought it was only the 7k sump that was different but the faq stated otherwise.

 

If you are getting a 5K or 7K out of a van, you may need a 4K Corolla sump, or you'll have crossmember clearance problems. Some people have reported that stock 5K sumps fit fine into Corollas.

[camerondownunder88]

Hi,

My 5K did this at about 7000RPM was found to be my ignition coil. I had points and was able to vary the resistor to get it not to by tuning coil.

 

Electrical Id susspect your advance vac system.

 

What cam is in it?

 

Currenlty I run 276 degrees duration cam and with twin down drafts I run 10.3:1 CR and a TRD CDI. I can set my base timming to 18 degrees at idle.

 

Any less it pings under load or when I put my foot flat to the floor and I lose all vac advance and the mechanical advance isnt graphed to the cam correctly. So motor misses a bit at 3200RPM and again at 3750RPM after that smooth sailing to 8500RPM.

 

Also my cam comes in at 3500RPM.

 

I know from my old electric dizzy it had a very aggressive advance weigh set up in it from stock to make torque for a van so if you have a bigger cam get dizzy regraphed might help.

 

 

As for sump I have a 5K sump from a van with no oil level sensor and it bottomed out on my KE30 and KE15 cross member nothign a hammer didnt fix. But first look at your engine mounts.

 

K motor mounts do vary between models some longer shorter etc. Are you running original KE70 mounts?

 

Cameron

[flamingheads]

The engine is a totally standard 5K with a downdraught weber and electronic ignition so no cam to play up.

 

I found that the one vacume hose going to the carb was blocked and have fixed the problem. If that doesn't fix it I have a spare coil I'll try.

 

I'm just making my tacho fit properly into my dash which is taking ages, then I'll take it out and see if I can work anything out.

[Clapped out]

Are you running a stock fuel pump? Could be that you're draining your float bowl and and thats why your pulling up.

 

+1

Edited September 24, 2010 by phatke30

[flamingheads]

Ok fuel pump makes sense. If I get one off ebay is there anything I should look for in a pump? What psi do I need?

 

Would something like this be ok?

[Old fella]

Mate, I`m not sure that I would go to the trouble and expense of an electric pump just yet. I ran a mild 4k with a gigantic cam and a 32/36 dgv and only used the stock pump. I had no drama pulling 8000rpm out of it and never a fuel shortage.

I suggest doing a quick fuel pump check by removing the fuel line from the carb and using a container to measure how much fuel is pumped in one minute while the engine is cranked over with the starter motor. (PLEASE DISCONNECT COIL LEAD) It might take you and a mate to do this safely.

The problem really sounds like a fuel pump because the motor will rev clean until it empties the float bowl and when you back off it gives the fuel pump time to catch up. I`m not suggesting that you try, but theoretically, the same cycle would occur if you held your foot flat again without changing gears.

I hope that this is a help.

You should have no drama sourcing a used fuel pump on this site. They`re like assholes. Everyone has at least one. My wife has two. One of them is sitting here typing.

Cheers.

[-=KE30=-]

http://cgi.ebay.com.au/FACET-SOLID-STATE-ELECTRIC-FUEL-PUMP-4-6-PSI-FP40106N-/140430915196?pt=AU_Car_Parts_Accessories&hash=item20b255b67c

 

Ive got this one in my ke30 just with a 4k and it seams fine at any rev range ^_^

[altezzaclub]

The electric pumps will pump a constant amount of fuel, but the mechanical pumps more as the revs rise and the original one must do the job if it is working correctly.

 

Problems come from damaged diaphrams in them and shit under the valves that prevent them from sealing properly. Ol'Fellas check to see how many L/min it pumps is the best check.

 

The only other way I can think of is to run the car as hard as it will go... Will it haul 160kph?? In that case the fuel supply must be good enough, and the hesitation is somewhere in the electrics.

[spoon]

valve bounce?