3.5 V8 hotwire, not starting

[v8hotwire]

Engine
1977 3500 V8
Hotwire fuel injection
Car has been running perfectly in this setup since 2008

Symptoms,
Starter turns well
Fuel pressure is good; pump starts, and pressure reads 38psi before cracking.
Spark exists at plugs; held plugs to earthing point around the car
Petrol is in the cylinder; not a huge smell coming through the exhaust though, so perhaps injector related

I have got Rovergauge up and running. Throttle is registering perfectly, temp gauges registering. no revs though when I turn the engine over. No fault codes being picked up.

Any pointers on where I should look next? I bet it's a loose lead somewhere. Anything I can check with a voltmeter?

Jim

[v8hotwire]

Thanks folks, makes good sense. I'll concentrate on the negative wire from coil to ecu next then.

Jim

[v8hotwire]

blitzracing said:

The ECU is fed from the switched side of the coil, so it gets 4 trigger pulses per engine revolution. You can do a really simple test to check if the ignition is getting to the ECU. Disconnect the king lead from the top of the distributor, and strap its connector near the chassis to make a spark gap. Remove the rotor and rotate the engine until one of the trigger lobes aligns with the pickup (as if you where going to measure the air gap). Then turn on the ignition and tap a screwdriver tip across the air gap to complete the magnetic loop. You should get a sharp crack as the coil fires the king lead, and the fuel pump should kick in to life if the ECU is getting a signal for about 3 seconds- it just needs a single pulse to do this. Its the same timed pulse you get when the ignition is switched on. If there is no pulse, you need to check the loom connections for the 6.8 k resistor that is in the loom between the coil and ECU.

Shown here half way down the page:

http://www.britishv8.org/Articles/Rover-14CUX-EFI....

I don't get continuation through the 6.8k resistor. But, I have a spare, and same. Is that cos the resistance is so high? One measures 7.2k ohms, the other 6.2k ohms (on my old voltmeter).

Jim

[v8hotwire]

Don't worry. I bridged the resistor, but still no revs registering. The white/black wire has continuation though, and there is spark. Hmmmm. One of my checks must be wrong.

[v8hotwire]

Thanks.

Yep, the ecu is powering up as it is registering throttle pot, temp etc on Rovergauge.

[v8hotwire]

Yep, all the way from coil to ecu connector, I've got continuity.

Hmmm.....

[v8hotwire]

Just tried new ecu, nothing.

Will try some easy start into the plugs, see what happens,

[v8hotwire]

Thanks mate.

Not done the EasyStart yet. But just had a thought. I noticed that the fuel pump kicks in when I'm cranking, so I am guessing injectors are firing, and am therefore thinking the ecu knows the car is cranking.

So, probably time to go back to checking the spark? Damn. I've already seen spark from each plug. I will check again.

[v8hotwire]

Right, just replaced all plugs. Old ones stink of petrol. :-)

But, battery is dead now, lol! On charge.

[v8hotwire]

"I did mention the pump bit at the start of the diagnosis...."

Sorry mate, the penny only half dropped with me.

I noticed the pump was starting with ignition on, but it had not occurred to me about checking whilst cranking.

Jim

[v8hotwire]

Well, seems to be dodgy leccy connection, as I sprayed engine cleaner on all the terminals at the starter motor, and at the fuse boxes, and it fires into life perfectly! When it all dries, it then fails to start again.

Am now in process of cleaning all terminals, and giving the loom in the engine bay a general tidy-up and re-wrap.

And RoverGauge all works as expected when the engine is running. Such a good piece of kit.

Edited by v8hotwire on Monday 30th July 19:54