Blocked Injectors?

[BrenG]

I had a post in the ignition section "It still won't start" my SD1 VDP EFi has not been run for over 12 months due to the considerable amount of welding it needed.

Despite trying for a few months the engine will not start - it splutters for a second or so and that's it.

New plugs, arm and cap have made no difference. I even removed the timing cover to check for a worn chain (thinking it may have jumped a tooth), valve timing was ok, replaced chain anyway. Timing marks on the pulley were around 15 deg. out, so I got no 1 to TDC and made my own marks on the pulley.

Battery is healthy (over 12 V when cranking), I have around 10V when cranking at the coil, but this does fluctuate. I have a spark at each plug. Coolant temp sensor shows 2.62 on the 20K ohms range on my meter, I assume this is correct for the current temperature.

However, I have noticed today that after cranking only plugs on 5 and 6 looked as if they had fired - they were black and smelled of fuel. The rest were dry. I have noticed that even a dose of easy start makes no difference.

Could it be that I have blocked injectors? The tank was removed from the car during welding, the fuel in the car is a few months old, I dont think it would have gone sour yet. However, any motorcyclists on this forum know about the peril of leaving old fuel in a bike - your carbs get gummed up.

Any advice appreciated - I am rapidly running out of ideas. As this is my hobby I don't have a lot of money to spend, but dont mind getting the injectors cleaned if it means the car runs.

[ramon alban]

I have a spark at each plug.

However, I have noticed today that after cranking only plugs on 5 and 6 looked as if they had fired -

they were black and smelled of fuel.

The rest were dry.

I have noticed that even a dose of easy start makes no difference.

Hello Bren,

Based upon the above evidence it does seem that your injectors may not all be firing.

You have observed sparks on all plugs so clearly the ignition is working but perhaps not in the right sequence.

Now to the nub! Two main reasons why all the injectors are NOT firing will be either

# ECU - is damaged or its multiplug connector is not making proper contact or

# Resistor Pack - is faulty or the connections to and from it are damaged/corroded.



Commonly over 80% of all flapper Efi system faults are due to wiring loom connections problems and air leaks into the plenum, In your case suspicion must fall on connections, so read my PDF available from here

http://www.vintagemodelairplane.com/pag ... ing01.html

If the resistor pack and/or the injectors are faulty, they can all be tested looking for the relevant article from this archive.

http://www.vintagemodelairplane.com/pag ... nts01.html

For a faulty ECU, substitution is generally th best test option.

Finally, its possible your ignition system may be set up wrong because the engine will not fire with the help of Easistart.

For that to happen perhaps the plug firing order is wrong.



Also - Worth studying both these articles:

http://www.vintagemodelairplane.com/pag ... ion04.html

http://www.vintagemodelairplane.com/pag ... ion05.html

[DaveEFI]

The injectors are in two groups - each having its own driver 'transistor'. If you wire an LED with a 1000 ohm series resistance across the injector you'll see if it is being fed, as the LED will flash at low revs (or cranking) and light continuously at higher. It's most unlikely several injectors are blocked. It is just possible the ECU was damaged by the welding - although this isn't as common as some think.

I'm a bit suspicious of the timing marks being 15 degrees out. That is more than an inch of pulley circumference. If your timing is very retarded it won't start.

[stevieturbo]

I did post some very basic tests to carry out in the last thread, none of which ever got a response.

I'll repost.

Basics first.

You say you have spark. So do you have spark ( on all 8 ), and at the correct time ? If you cannot confirm this, there is little point continuing.

You say you have fuel....so are the plugs wet or dry ?

If soaked, bin them and fit new ones.

If totally dry...then I would have to say you do not have sufficient fuel to start an engine. So why do you believe you have fuel ? Investigate why no fuel is being injected.

Are the injectors getting a signal ? Very easy to test with a voltmeter with either pulse width, or duty cycle.
Or you can remove the entire rail and injectors and do a proper visual that all 8 are spraying.

If no fuel, is the pump running ? Are the injectors receiving 12v ?

Once the above have been confirmed and rectified if required, start engine.

[BrenG]

Gentlemen,

Thank you for your replies.

If I push the flap in the AFM I have fuel under pressure - so that side is ok.

You will have to bear with me - my knowledge of auto electrics before this week stood at checking batteries.

It is possible that I have damaged something - I remember welding for a minute or two and realised the old battery was still connected. I then disconnected the thing.

I know a chap locally who breaks SD1's and range rovers so I will see if I can borrow an ECU and resistor pack and try substituting them.

[Quagmire]

If you have verified that your injectors should be working electrically - i.e. they are being pulsed then they may be stuck closed. I had exactly this a couple of weeks ago when I finally fitted fuel injection to my 3.5.

I had 7 of my 8 injectors stuck closed!

If they are opening not only will they make a definite click noise, but if you touch the body of the injector you can easily feel the tapping of the injectors as they work away.

A couple of taps with a soft drift and a hammer on the body of each soon freed mine off. I tapped them whilst my Dad pulsed them on and off with the momentary switch setup we have for our injector test rig. The car has done a few hundred miles on petrol troublefree so far.

[SuperV8]

I also had 6 of the 8 injectors gummed up and not working.
I used a small battery accross the terminals to check if they opened. You can hear them click if they do. 6 failed that test so I took them out and replaced them/ or you could clean them.
It still wouldn't start and this turned out the be the mini timer connectors on the injectors weren't connecting. you can check the continuity at the ECU plug end. And open injector circuit is wrong. A quick tweak of the recepticals in the connector to close them up and she started.

Tom.

[DaveEFI]

What 'small battery' did you use? Flapper injectors have a resistance of 2.5 ohms. As installed they each have an 6 ohm series resistor from the + 12 volts supply, and the ECU grounds them in banks of four. Very few dry batteries could supply enough current. And 12 v direct from a car battery could fry them.

[SuperV8]

I think I used two AA in series to make 3v. This was enough to open the injectors. Then rigged up a small test bench using an airline and the battery to test each injector. Yes I didn't use 12v as this may damage the coils.

I have lots of bits spare for the flapper engine, resistor pack/ecu/injectors etc... PM if you need anything?

Tom.

[DaveEFI]

I think I used two AA in series to make 3v. This was enough to open the injectors. Then rigged up a small test bench using an airline and the battery to test each injector. Yes I didn't use 12v as this may damage the coils.

3 volts at the max current a couple of AAs can supply may not be enough to open every injector. To be sure one or more is faulty, you'd need to use 12v and the correct series resistor.

I have lots of bits spare for the flapper engine, resistor pack/ecu/injectors etc... PM if you need anything?

Tom.

I'm ok thanks. Have a MegaSquirt so don't need any of the more dodgy bits from the flapper system.

[SuperV8]

I'm ok thanks. Have a MegaSquirt so don't need any of the more dodgy bits from the flapper system.

That offer was actually ment for BrenG.

Tom.