390SE has poor hot starting. Any ideas?

[ed_crouch]

Also, the car doesnt start very well when hot. It cranks over for several seconds, and usually requires a good squirt og throttle to get it into life.

Sometimes even then it misfires its way to 900RPM, rather than flaring and then settling back to idle.

I reckon this might have something to do with the poor performance at high RPM as in my other post...........

Any learned people out there able to help??

Ed.

[jchase]

My previous 390se (sob-sob), with NCK engine has a 'didled' with Air Flow meter, so you need to have the fuel pressure set to a suitably 'diddled' with value (Generally over 250kPa, but less than 300kPa seems to be fine). TVR generally put adjustable ones on the NCK engine, and these need adjusting often.

-Jim

[numbnuts]

It could be running very weak!

[ed_crouch]

Yep, AFM has defo been diddled with, as there black goop around the cover.

Havent ever checked the fuel rail pressure, but have bought a 0-7 bar fuel pressure test gauge, so will check it out.

the 250 - 300kPa pressure: is this with the vac feed at atmospheric pressure, or on deep manifold vacuum?

Thanks for you replies!

Ed.

[TVR 3X]

Is the cold start injector still connected.

The one on the top of the Plenum. It is not normally needed in the UK climate and can be left off if it helps.

Russ

[jchase]

ed_crouch said:

Yep, AFM has defo been diddled with, as there black goop around the cover.

Havent ever checked the fuel rail pressure, but have bought a 0-7 bar fuel pressure test gauge, so will check it out.

the 250 - 300kPa pressure: is this with the vac feed at atmospheric pressure, or on deep manifold vacuum?

Thanks for you replies!

Ed.

This is usually the static pressure, obtained with the fuel pump running, but not the engine. You can disconnect the vacuum pipe, but your vacuum gauge might get confused by the pulses in the line with the engine running. BTW don't trust those cheap-o 52mm gauges in glycerine, I had one and it was 20% off versus my very expensive digital gauge.

When I first got my 390se it was bit slow, the fuel pressure was at 180kPa! after adjustment the car was ballistic!

My 390 would run very rich at idle circa an AFR of 11, which is way too rich really, but backing out the idle mixture screw made little difference. ISTR the 390 has solid lifters on the early Andy Rouse engines, so you may just need to adjust the push rods (never took the tappet covers off mine to find out)

-Jim

[danny hoffman]

Have a look at the thread I started about the probs on my 350i, evey check under the son was suggested

[dickymint]

Starting problems when hot - could be the ignition amp/module (black box on the dizzy).

[adam quantrill]

Could be the engine temperature sensor!

(At last - sanity restored - I got this one in first...)

[ed_crouch]

This is all really good stuff, so thankyou all for your help. Im going to visit the car tomorrow (its hibernating), and will hook up the fuel pressure gauge to it, and see whats occurring in the fuel rail. Had a rudimentary go at calibrating the gauge today by connecting it up to my airline via 1/4BSP fittings. It showed exactly the same pressure as my compressor gauges, so I guess its accurate (Jchase did warn me that sometines the cheaper pressure gauges can be inaccurate...), as the chances of both gauges on my compressor AND the fuel pressure gauge being wrong by the same amount are small...

Anyway, Im really hoping to see only 18 - 20 PSI on the gauge, cos that would probably cause both the performance and starting problems.

Heres hoping...

Ed.

Edited by ed_crouch on Friday 2nd March 16:57