Ferris the Cat

Bear with me on this, but grateful for any advice please.

UK 928 S4 1988 MY (no Ignition Circuit Monitoring Relay)

X pipe fitted and no cat

Pootling along and without warning it lost power and felt bogged down, as if one of the distributor king leads had come loose. I was close to home so managed to feather the throttle and roll into the garage. Since then, turns but does not fire.

I am pretty handy with the spanners, but a bit of a noob with anything involving electrickery.

To date, I have:

1) Had the LH and EZK tested by JDS and all good
2) Jumpered the fuel pump and heard it run. Fuel pump, filter and intank (replaced pump for strainer) are all less than 12 months old.
3) All relays ok, but replaced anyway, Fuses good
4) I noted no movement of the tacho so replaced the CPS, but if the pump runs, the CPS must be good
5) Checked my vacuum lines. No smell or sign of fuel, but a couple of ends had split so replaced those. That said, I am not convinced and intend to try a few more starts and sniff again
6) Both coils tested and resistance across primary and secondary are fine
7) Battery is pretty new
8)I Have checked the various grounds and the battery terminals
9) Using an ignition gun, had spark at the plugs.
10) When I turn the ignition on, I do hear some clicking from the engine. Noid light probably the next purchase.
11) Temp II sensor replaced

I think the next step is to check the fuel pressure. It does smell of fuel when I try crank it (except when I do the foot to the floor start). I somehow need to get the correct fitting for the fuel rail but these seem to be unobtainable. I assume a generic 12x1.5 female globe fitting will not work. I do think it is the regulator or one of the dampers, just by the way it went lumpy on me.

I have ordered new ignition amps, these are on back order so won't be with me for a couple of weeks.

I did try and check for voltage in the 35 pin connector- I did it by using the relay box cover bolt as ground and taking the live from the respective slot. Did I do this right - I am a bit crap with the AVO meter?

I also got busy with the de-oxit.

Spideysense says the smell of fuel and the way it grumbled for 3 miles then died is a fuel issue.

All the belts are good, in date and the TBF checked in last 12/18 months and a Ritech clamp fitted anyhoo (Engine was rebuilt in 2020).

Thanks you for reading.

Mrmerlin

OK lets get more info here from your clues,
first if you turn the key to run, are you saying that you hear a clicking from the engine?
Like the injectors are clicking without the engine running?
If so the the LH has failed,
try your LH in another car.

Has the LH been rebuilt?if not then it needs it,
make sure the EZK is also sent in/ checked.
NOTE I know you said JDS checked them but if they have not been rebuilt then they could be bad.
Are the grounds tight at the back of the engine V?

What parts were replaced on the intake refresh when the engine was rebuilt in 2020.
Was the MAF rebuilt?

Did you perform the relay test for the running relays?
Please perform the following test ,
kneel at the CE panel,
then touch the following relays as you turn the key to the run position.
X bus,
LH,
EZK,
FP, this one may need engine to be cranking .
what your wanting to feel is each of these relays clicking on.

Replace the fuel pump fuse.
remove and clean the wires at the battery make sure to clean every connection.

Please post engine pictures to ascertain condition

Ferris the Cat

Thanks Mr Merlin - I'll work through that list and also post some pictures.

The rebuild was bottom end, so most of the top end of my old engine was transferred across.

MAF has not been rebuilt - so that is one to test. I did try starting with the MAF unplugged, but given it was probably rebuilt at least 15 years ago, I think I will send it out for a rebuild anyway,

The EZK an LH were both tested by JDS and both got a clean bill of health. WE discussed a rebuild and the advice was that both didn't present like they needed one.

I will work through the other tasks and report back.

Thanks again.

Mrmerlin

whats the condition of the temp 2 sensor and it connector?

Jfrahm

What do the plugs look like?
Does it catch if given a shot of starting fluid or carb cleaner (or fuel)? You can inject this into a vacuum line to get it in downstream of the MAF
Odd that you are not seeing the tacho twitch but if the fuel pump runs based on the LH signal then there is probably a crank signal.

Ferris the Cat

I replaced both. The connector was a bit crusty. I will double check there's no break upstream. I found the resistance readings I should see in the WSM. I think I have figured out how to do that - it's a journey this electrical stuff .

Thanks.

Ferris the Cat

Yes. I thought I had cracked it when I saw no tacho bump, but the pump was certainly whirring away when I tried cranking it.

I am going to go back to first principles, and have someone turn on the ignition while I physically check the pump, just to make sure I am not going mad (which, is possible ).

FredR

When was the LH test carried out?

The LH unit is notoriously fickle and original build items can fail at any time without warning.

Clicking injectors is a classic sign of LH failure. If the LH unit is still in original build state then failure has to be a high probability.

EZK units are very reliable but even those are now showing signs of failure.

Ferris the Cat

Hi Fred - last week. I sent them off to be sure and it seemed sensible given I've 20 years history (owned it 5) and no sign of them being tested or rebuilt. Mike at JDS put them through the wringer and they came out ok.

Mrmerlin

the LH could have just failed .
Please answer this question,
when you turn the key to run do you hear the injectors clicking ?
What is clicking

jchasty

I went through a similar experience - poor hot start and idle.

After going through the same fault finding process (over a couple of years!) it turned out to be the MAF!

FredR

OK- now the chronology is a bit clearer.

Given the sudden onset of the problem that suggests to me some elecrical continuity issue may be in play. You could possibly have a MAF issue but at the moment I would suggest you might look into the wiring conditions as the loom enters the MAF plug. That is a tight radius bend and commonly goes to ratsh*t in that location. If the signal is corrupted the MAF goes into the limp home mode and gives a fixed signal that fuels correctly at about 2k rpms lighty loaded. Pulling the boot back [it will probably disintegrate] and opening up the heat shield [that will be like bakellite] might expose something going on.

A "stock test" is to pull the MAF plug and see what happens- if nothing changes then the problem is likely MAF system related.

Ferris the Cat

Thanks chaps.

I will do the click test and also have a good explore of the MAF and report back.

Petza914

If you pull the vacuum hoses from the FPR and FPD, do the hoses smell like fuel or have liquid fuel in them?

Ferris the Cat

They didn't when I last turned it over, but I tried the foot to the floor trick, so will try again turning it over as normal.