350i Starting Problems

[Benjamico]

I recently bought a slightly delapidated 350i with a friend with the hope of getting it on the road ready for Le Mans this year, it had a replacement engine in place but not wired or plumbed.

We have now installed all the ancillaries and wired it up as best we can, however we can't get it to start.

We have checked the spark and it is strong, we have also checked the fuel is being delivered and (after a little head scratching and re-wiring) the fuel pump is working as it should be.

We think that either we have the timing out of sync or the fuel injectors possibly aren't firing correctly. We used a noid light and there seems to be a (possibly weak) pulse on each fuel injector, it also appears that the injectors are firing too rapidly in comparison to the spark plugs.

As we are starting to run out of time, are there any obvious things we may be missing or are there any TVR specialists anybody can reccomend in the Hertfordshire area? Happy to pay for their time if they have the ability to diagnose the problem.

Any help or info would be very much appreciated.

Thanks

Ben

[Benjamico]

Thanks Adam, that explains the firing pattern we saw, however the light was extremely dull.

Silly question possibly, but when checking continuity of earth, we found no earth on either side of the conector of each injector, do you know if this is this normal?

Thanks again

[Benjamico]

Thanks Fettler, plugs were dry, so I'm guessing the signal must be too weak to fire the injectors.

I've got some RV8 Efi drawings from doing a google image search.

When searching, I've seen a few references to a resistor in the coil wiring, I haven't seen a resistor and wonder if this could be partly responsible?

[Benjamico]

Thank you both.

Adam, I've just been out and tried your suggestion with the throttle twist. It did indeed cause the injectors to click, but when I pulled out a spark plug and it was still dry.

The fuel pump is definitely delivering fuel so I'm pretty stumped!

[Benjamico]

Thanks, I just double checked by pulling the main fuel hose off and it is definitely pumping a good quantity through it.

[Benjamico]

350zwelgje said:

You probably have, but can check if the fuel pressure regulator is after the injectors/at the end of the fuel rail (not before or the entry of it). Or even feed and return line connected to the right points of the fuel rail/fuel pressure regulator.

More people have had issues with the fuel pump: provide power and it works, connected to the normal wiring it doesn't work. You can try to run two extra wires direct from the battery, when the pump is running then try to start the engine to exclude the normal wiring & setup.

Rob

I don't think my brain was in gear when I first read this, I've now caught up!

The return feed is connected to the FPR with the delivery hose connected directly to the rail.

I pulled off the return feed hose and tried starting it with the return blocked in case the FPR is stuck open but no luck!

[Benjamico]

I spent a bit more time with the wiring diagram and a multimeter this evening, I'm now pretty convinced it is the injectors not getting a strong enough signal.

I put a noid light between the yellow +ve wire of the injector harness and a good earth and the light came on very brightly. When I cranked the engine and put the light between the two terminals of the injector plug it gave a really really dull pulse.

I have checked all the earths to the ECU and all seem OK, do the symptoms correlate to any known issues with the wedge?

Thanks

[Benjamico]

adam quantrill said:

Have you tried the rotate throttle and click test I mentioned above? If they don't click that will double-check the theory.

The circuit returns through the power resistors so the most likely scenario is the single brown/orange wire is not connected all the way through or the relays aren't working. THis will kill both banks. If one bank is working and one isn't, then the best bet is the ECU power transistors for that bank.

If the click test causes obvious clicking then change tach (geddit?) and make sure the ignition pulses are getting to the ECU to tell it to fire at all.

I tried the click test and it does click on both banks, there is still no fuel delivery into the cylinder though, it's very strange!

I have also tried removing the distributor and spinning the shaft, this also genegates clicks but again no fuel delivery. There is really good fuel pressure at the rail too... very confusing!

Maybe I do need to change tach... has anybody got a box of matches they can lend me?!

[Benjamico]

Firstly thank you one and all for your replies!

I have just spent a little time tinkering and the cold start injector is definitely firing as it should.

I swapped the harness from cylinder 4 and 6 and tried it on the cold start injector and it doesn't fire so we have progress!

Wedg1e you mention the importance of the earth, one of the initial problems was that the fuel pump and coil weren't earthed, we found one thick black wire and two thinner black and white wires that came out of the bulkhead we attached to the back of the cylinder heads. Are these one and the same or should we be looking elsewhere on the loom for the earth wires?

[Benjamico]

I'll try and describe how I've wired it best I can...

The white wire wire with a black stripe is connected from the ignition amp to a connector on the loom just by the air flow meter and resistor pack.

The two wires I meant are black with a white stripe and come out through the bulkhead into the engine bay both go into a single crimped ring connector.

Hope that makes sense or have I shorted the signal?!!

[Benjamico]

Thought I should share a pic of the work in progress...

[Benjamico]

adam quantrill said:

From here I can see that the AFM air hose is not connected.

All together now... it won't run without it....

Perhaps some close-ups of the engine bay?

Sorry I should have been more specific, that is a picture of it before work began!

Since that picture we have made some progress... Here are the highlights!

All coolant / air / fuel hoses have been connected / replaced.
Alternator / pulleys / starter motor / exhaust manifolds / engine mounts installed.

I will get some pics at the weekend and post them up for all to see

[Benjamico]

Further progress has been made...

I'll start with the good news, we took the injectors out and they are also firing as they should.

We reset the timing and still nothing.

Next up we removed the rocker cover to double check we were on the right cycle... Then came the bad news, as we cranked the engine the rockers weren't rocking on three out of four cylinders!

Back to the drawing board!

[Benjamico]

So much for the "reconditioned" engine it was supposed to have...!

We bought a gauge and did a compression test and it barely registered 2bar / 25psi on any of the cylinders.

We also took off the rocker bar and tried to free it all up a bit and gave the valves a tap to make sure they weren't stuck solid but to no avail. The push rods were all straight so the worn lobe theory would definitely make sense.

We will try and source a replacement engine in the meantime and possibly strip the current one to see if it's worth saving, but it looks like it may take longer than the time we have for Le Mans this year!

[Benjamico]

Thats a fair point, just my slight worry of throwing good money after bad, although to contradict myself a replacement engine is also an unknown quantity.

I've got some thinking to do!

[Benjamico]

Back with a bit of an update tonight.

I spent a few hours taking off the inlet manifold etc. to get a good look at the camshaft and it is indeed rather worn, well I say rather worn... it has absolutely no lobe half way down, it's completely round!!

So camshaft / followers are definitely on the list of things to be replaced. I managed to pick up a set of recently refurbed HRC 2479 heads for £30 too.

It's going to be interesting to see how the cylinders look once the heads are off

[Benjamico]

Thanks for the tip Adam, will remember that one

Agreed the heads could be another can of worms, but one of the exhaust stud holes was dodgy and I'd rather not mess with helicoils or having to re-tap and put a bigger bolt in. Appreciate this will mean the use of a composite gasket and follower pre-load may have to be adjusted and air fuel ratio etc.

The missing lobe was on the drivers side in the centre, I will be trying to check there is not an oil starvation problem like a blocked journal, the other possibility I considered is a seized tappet, but I'm not sure how likely that would be?

[Benjamico]

Got the heads off and the camshaft out this evening, bores look pretty good so I'm going to rebuild rather than replace.

The lifters don't seem to want to come out, is this normal or a further sign that things aren't right?

One suprise was the timing chain, there was about 40mm deflection in the chain... I'm guessing that wouldn't have helped the situation either!

[Benjamico]

Thanks Leigh, thought this would be the case, I just didn't want to force them out without checking first.

They are definitely on the list for replacement!

[Benjamico]

I'm starting to get the feeling you are somewhat of an oracle when it comes to wedges Adam!!

I pushed them high enough to get the camshaft out, but that was as far as most would go, I did think that getting them out by pushing them down looked easier, but I'll have to think of a way of catching them first!