3.5 V8 won’t start

Puchacz · Oct 25, 2019

Evening all...

Got a 3.5 EFI V8 in an 89 RRC that shows no signs of wanting to play.

It has run perfectly up until today. All of a sudden, showing no inclination to start. It’ll turn over and give a very occasional cough but won’t fire up.

It’s getting spark.

I can hear the click of the injectors when I manually activate the flapper with the ignition on.

I can’t seem to hear any fuel pump noises from the tank area. I’d imagine I should when the ignition first goes on?

The fact that the engine went from running perfectly to not at all makes me hope it’s something relatively simple.

Anyone got any suggestions on best things to try?

Thanks a lot.

wireman · Oct 25, 2019

You maybe onto something with the fuel pump. If you can normally hear it running and now you can't then it might be broken or maybe a lose wire/bad earth. Try spraying 'easy start' or brake cleaner into the intake manifold, if it runs you can rule out your electrics.

Ratae · Oct 25, 2019

Mine's a 1986 3.5EFi Flapper so the set-up should be the same as yours.

If you operate the flap with the ignition on & the tank pump isn't running then the issue is the pump or its wiring.
Prop the flap open with the ignition on.
Check the fuse is OK & that there is power to the fuse.
The plug for the pump is accessible in the nearside rear wheel arch - remove wheel for easy access - & is a cylindrical black thing.
Check there is power to the socket - unplug the pump & use a test meter on the vehicle socket. Check the earth side is OK.
If you get a more-or-less battery voltage reading then re-check using a test bulb. Reason for that is I had the same issue with mine and whilst the meter showed battery voltage the bulb didn't light. Using a pin to work my way up the +ve wire revealed corrosion in the wire had reduced the end to a couple of strands - enough for a digital multimeter to show battery voltage but not enough to carry sufficient power to make things work.

If the fault is the wiring you MIGHT be better cutting the plugs off & hard-wiring or replacing with a modern waterproof connector - bearing in mind that that will involve cutting the pump plug off as well which obviously would void warranty on a new pump. The metal part of the standard connector are available but can be a PITA so I finally opted for cut & rewire.

If that checks out OK then using a spare battery - or very long test leads, I have several with small crocodile clips at each end - apply power to the wires going to the pump. If it doesn't run then the pump has failed or there is a fault in its wiring.
Unfortunately changing the pump is a tank drop on these - unless you cut a hole in the floor.

Puchacz · Oct 25, 2019

Thanks chaps.

Ratae, thanks very much for that. Will get on the case. Are you able to hear the pump run on yours?

Puchacz · Oct 25, 2019

While I’m here, sorry for the bonehead question but where is the fuel pump fuse located? I was looking last night and all I could find in the fuse box in the dash was one fuse with a fuel symbol on it, is that it?

Ratae · Oct 25, 2019

Puchacz said:
Thanks chaps.

Ratae, thanks very much for that. Will get on the case. Are you able to hear the pump run on yours?

Yes, but the ignition must be on AND the flap propped open when carrying out the tests as the flap switches the power to the pump when running.
You may need to open the fuel cap & listen as they can be quiet - a humming sound. I had one fail - long before the wiring issue - and it sounded rougher than a rough thing.

My tank has the pump on top & the level sender as a separate unit in the nearside side of the tank. If yours is the same & you replace the pump the pickup tube on the pump is adjustable for length. I found that out when I replaced a leaky tank - fuel gauge showed just on the red but the engine said 'No fuel'!
Subsequent measurement showed the new tank to be slightly deeper than the old.......

Ratae · Oct 25, 2019

Puchacz said:
While I’m here, sorry for the bonehead question but where is the fuel pump fuse located? I was looking last night and all I could find in the fuse box in the dash was one fuse with a fuel symbol on it, is that it?

That's the one.

Ratae · Oct 25, 2019

Whilst the easy-start suggestion earlier would show it's not an ignition issue if the engine runs as you are squirting it into the intake be aware that it carries a risk of a flashback & the flapper afm is easily damaged by that as the flap will be blown shut & the pressure can then take it apart.
More commonly seen on LPG conversions that use a gas ring to introduce the gas into the intake & is the reason I have an arrestor in mine although I changed from the gas ring to a BLOS some years ago.

Ratae · Oct 25, 2019

Quick note.
The fuel pump on the flapper is initially energised on cranking by a relay and then the electrical supply is controlled by the flap in the afm. Hence why you need the ignition on & flap propped open during testing.
I think the relay is one of the 3 in front of the ECU (assuming 4CU) under the driver's seat but as - so far - they've not caused me any trouble I couldn't say which one.

Puchacz · Oct 25, 2019

Extremely helpful, thanks again.

Puchacz · Oct 25, 2019

Update on this - the pump works if connected to a 12V source but is not running with the ignition on and the flapper held open.

There is 9V at the fuse and at the fuel pump plug connector when the engine is turned over which I’m guessing is battery voltage under starting load.

It would appear then that the pump probably is running with the engine turning over but it definitely isn’t with ignition on and the flapper open. Could this be the problem? Is it definitely supposed to run in this configuration?

Any help much appreciated.

norseman · Oct 25, 2019

Re. the suggestion of 'cutting a hole in the boot floor'
You'll likely find that your floor is riveted in place & is (I believe) alloy. Drilling out the rivets & removing the floor would be safer than cutting a blind hole as the top of the tank is very close to the underside of the floor

Ratae · Oct 25, 2019

Puchacz said:
Update on this - the pump works if connected to a 12V source but is not running with the ignition on and the flapper held open.

There is 9V at the fuse and at the fuel pump plug connector when the engine is turned over which I’m guessing is battery voltage under starting load.

It would appear then that the pump probably is running with the engine turning over but it definitely isn’t with ignition on and the flapper open. Could this be the problem? Is it definitely supposed to run in this configuration?

Any help much appreciated.

Yes. That's how it's supposed to be powered once the key is released from the cranking position to its normal ignition on position.
You should be seeing battery voltage(ish) at the connections. As I said earlier, a digital multimeter will tell you you have voltage but NOT that there is enough oomph to run the pump which is why you need to use a test bulb. If the bulb doesn't light there is either a fault with the battery or the wiring.
What voltage is showing with ignition on & flap propped open?
What voltage is showing at the battery?
What are you using to measure the voltage?

ETA. Be an idea to fully charge the battery with a battery charger before continuing, just to be sure its delivering full power.

Ratae · Oct 25, 2019

norseman said:
Re. the suggestion of 'cutting a hole in the boot floor'
You'll likely find that your floor is riveted in place & is (I believe) alloy. Drilling out the rivets & removing the floor would be safer than cutting a blind hole as the top of the tank is very close to the underside of the floor

Early ones are alloy & riveted in. Mine is. It doesn't have a hole to access the fuel pump.
Later ones are steel & spot welded. They MIGHT have an access hatch.
If you do cut with the floor in place, be very careful as the pipes from the pump are just under the floor. I wouldn't use an angle grinder, far too many sparks for one thing! I used a semi-circular metal cutting blade on a Fein Multimaster.
This worth a look: https://forums.lr4x4.com/topic/76252-rrc-boot-floor-replacement/

Puchacz · Oct 26, 2019

I was using a multimeter to check the voltages.

Have now plugged in a test light into the fuel plug connector as you suggested and getting similar results - it’s lighting up bright on cranking but not on with the ignition on and flapper held open.

I’ll check battery voltage later, it is fairly new though and has been charged since this sorry saga begun.

Thanks for the step by step Ratae. Have just got this vehicle after years of 200Tdi Defender ownership so not particularly familiar to jump in and troubleshoot myself!

Cheers

Puchacz · Oct 26, 2019

Anyone got any idea what this is? It’s in-line with the fuel pump power lines. Connections seem slightly dodgy.

Ratae · Oct 26, 2019

No. Has something fallen off the other end?
Where do the red & the other wire (can't make out the colour) go?
Any wires in the other end?

Puchacz · Oct 26, 2019

I think it’s a red herring anyway. After looking at it it’s just some kind of plug extension to the fuel pump power wires.

I’m really confused to be honest mate.

Every spark plug is firing strongly.

The plugs looked wet and smelled of petrol after being cranked for a wee while.

Battery voltage after an evening of cranking is at 12.2 off load. Charged up earlier was 12.7.

Voltage measured at the pump plug with ignition on and flapper open is zero. With the engine cranking it shows 9V (approx 1V less than battery voltage under cranking load).

The pump runs with with 12V applied to it from a separate battery - even after running it for 30secs or so and then continuing to power it while cranking the engine it showed no more signs of life though.

The injectors can be heard firing with ignition on and flapper opened.

The fact the pump isn’t running with the ignition on and flapper open seems the biggest clue. Any idea what that would point to? ECU fault of some description?

Ratae · Oct 27, 2019

Possibly. The 4CU has something of a reputation. This worth a look:
http://www.carelect.demon.co.uk/rrp1.html
I've had several 4CU ECUs die in the time I've owned mine, but none have shut the pump down.
Sudden very rough running &/or big clouds of black smoke from the exhaust have been the symptoms.
Substitution for a known good one would be worth a try. They do come up on ebay but you've no idea whether they're any good.
ETA. I have several different part numbers on the 4CUs I have & have had no noticable difference between any of them. I did email Lucas some years ago & their reply was much the same. I suspect there might be minor differences but as I say nothing that I noticed.

Note that the 4CU only controls fuelling & has nothing to do with the ignition - as I also have LPG when on LPG mine will run with the ECU unplugged.

Not had an issue with the AFM, but as opening the flap should power the pump I wonder if there is a problem with yours. Try a wiggle test on its plug - as in give it a wiggle to see if anything happens & consider cleaning the plug connections.

Not unusual for them to be converted to the later hotwire system & I'm given to understand it isn't a difficult job but haven't been involved with one so don't know the procedure.

When I had the pump connection issue if I connected a battery direct to the pump the engine would start & run.

I think you're now into the checking everything through with a wiring diagram.

Puchacz · Oct 28, 2019

Update on this... 8 new NGKs and she’s running like a champ!

Thanks for your efforts Ratae.

P.S. I realised after I posted, what I had assumed was the flapper was actually the throttle - the fuel pump did run with the flapper held open.

3.5 V8 won’t start

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