Engine failure after Tank replacement

[KaeptnNemo]

Hey guys, I need your help, I am absolute dersperate...

I changed the fuel tanks on my 92 Esprit SE HWing, because they were rusty. After puttinh everything back together, the engine won't start. There is a spark on each cylinder, the fuel rail has enough pressure, but it looks like, the injectors do not open. What went wrong???

What I did:

I opened all electrical connections on the right hand side. Obviously, I took to few pictures, so I am not sure about the electrical connections.

There are quite a lot plugs, that do not have a counterpart or are connected to anything. Please confirm, that this is normal.

 

I tried to access teh ECU via TECH-1, but i cannot get any data out of it. Even no battery voltage (which is definitely there at the ECU, mesaured by Voltmeter) can be read out.

Trying the fied diagnostic mode, the check-engine light blinks once after bridging the ALDL-Connector and then stays lit.

 

I have no idea, what else I could check. My guess is, that one connection is wrong or missing.

Is the ECU so sensitive, that it could have gone to heaven for some reason?

 

Any advice appreciated 😕

 

Patrick

 

[jonwat]

22 minutes ago, KaeptnNemo said:

I tried to access teh ECU via TECH-1, but i cannot get any data out of it

Download Freescan in order to read the codes.

[KaeptnNemo]

I guess TECH1 should do the same job. And it did before...

But I cannot read any data or codes.

 

[Sparky]

Trying to read the ECU wouldn't be my priority.  It was running, taken apart, reassembled and now it's not running.  So it's 99%  something you didn't reconnect.

How did you check spark, fuel pressure and injector opening?

[KaeptnNemo]

I took the Spark plugs out, and saw them firing.

I measured 3.6 bar at the fuel rail.

I used a Digital Voltmeter to measure the Injector Voltage, but there was not pulsing any Voltage, neither at the Injector nor at the Connector on the ECU.

 

 

[Sparky]

So start investigating all connections.  Especially that fun stuff on the right with the boot floor.

[KaeptnNemo]

I am going to recheck everything. Problem is, that the wiring diagrams do not really help on where which harness should be connected or which plug has no connection, etc... 😕

Hopefully i did not damage one of the harnesses... I am wondering, why the fuel pump relay only gets 5.5 Volts and starts vibrating...

 

[Escape]

I was worried reading the title that your engine had failed. 'Luckily' it's only a starting issue. And after doing work, so very likely to be a connector or fuse not plugged in correctly. 

You already found a smoking gun with the relay. Try putting a jumper on it and see it the engine starts that way. If it does, a bad connection to that relay is most plausible, or it could be a bad relay.

Fingers crossed you'll be up and running in no time. 😉 

Filip

[ragingfool35]

the fuel pump relay gets 5 volts at coil or terminal 30? I recently replaced all relays with units with diode across coil and discovered that not all the sockets were wired for 85 being positive (and also saw in wiring diagram that the starter relay has an external diode for coil).  car wouldnt start until i remedied the situation.  whatever the case you will have to examine every connection you touched

[KaeptnNemo]

What if….

there is a small damage in the harness!? A crack, a short….

i guess I am going to measure all wires between the ECU and every point where it should go…

 

next thing, I was thinking about, is the ventilation function. If the throttle is fully open, no fuel will be injected. But that requires, that the TPS is fully open, and it is not…

looking forward to it 🤬

 

 

[Escape]

Interesting reasoning about the TPS. I wonder if it isn't connected properly, it could give a false WOT reading?

In any case, I would start by jumping the relay, as it's the easiest thing to do and at this point the most likely cause.

[martin putz]

Hallo, bei mir war es dasselbe- nach der Restaurierung- unter anderem wurden auch die Tanks getauscht hat es sich letztendlich herausgestellt ( nach langer Fehlersuche bzw. Tausch von sämtlichen Sensoren) dass das steuergerät defekt war.

Tipp! Kontakt mit " lotus engineering " herstellen- der ist sehr freundlich und hilft dir gerne weiter. 

Hätte ich sofort diesen Schritt getan, hätte ich mir sehr viel Zeit und Geld und Nerven gespart....Mfg.Martin 

[KaeptnNemo]

Hast du Kontaktdaten zu Lotus Engineering?

I am wondering how I could check the ECM on the test bench!?

supply voltage, ground and then receive serial data from it?

or does it need more input before responding? 
 

 

 

[LotuStuart]

Id want to be sure all my electricals were connected properly-and that all my fuses were good-before touching stuff that was working fine before.

I'd be particularly wary of touching the ECU.

 

[KaeptnNemo]

I just read a thread in the  parallel forum about a flickering fuel pump relay, which was a problem of a loose ground connection to the transmission housing. 
That really sounds all more like a connection problem (even because I lowered the engine, maybe something ripped off or got loose).

I’ll investigate on that and let you know!

 

 

[martin putz]

https://espritengineering.co.uk/services/ecu-repairs/

[Jacques]

Patrick, may I ask a dumb question?

What about the ground wires underneath on the side of the tanks? Did you do those?

What if you attempt start with out the two fuel filler caps on? I've seen a case where there was negative pressure, so fuel wouldn't be sucked up.

Also, When you did the tanks, you have worked with the fuel pump which is submerged into one tank. This pump have a small filter on it, sometimes a little green mesh, which can come apart and into the pump and block it. I had that problem and no start was possible, until I found that green mesh as the culprit. Started right up after that was removed.

Also, if you change the pump as it can be bad over time, most will, there's a part that you do not reinstall on the new pump. Just saying.

Please check these things first.

Old battery btw? Not the cause probably, but low voltage may trigger all sorts of funny problems. But that's another story.

Cheers,

Jacques

 

[KaeptnNemo]

Hey Jacques,

I did not renew the braids, but I refitted them.

I replaced the fuel pump, but that does not seem to be the problem, as there is fuel at the rail. 
Battery is not a year old und is on a battery conditioner right now.

i think, the flickering fuel pump relay is a clear sign for a contact problem.

So I opened all connections and used Contact Spray on it. It’s drying right now, before I reconnect everything.

I’ll give it a try tonight or tomorrow.

As I said, the CEL was not blinking 12 when in diagnostic mode, but only a short pulse and then steady light.

Possibly I did the diagnostic wrong because of a misunderstanding. I bridged the diagnostic line only for one second but reading the procedure again and again, it might be, that the bridging needs to be permanently for the time of diagnosis.

I am going to try that out as well!

 

Stay tuned 😉

 

Patrick

 

[Escape]

Again, jumper the fuel pump relay to get it out of the equation. If she starts, rejoice! Replace the relay (they can go bad) and only then start looking for the bad connection. I'm a big fan of the path of least resistance and expense when problem solving. 😉 

A missing or poor earth is a good call though, we've all been there. For me, it was the ones on top of the bellhousing. 😳

For field diagnostics, the ALDL needs to be bridged during the entire test. You should also hear the fans come on.

[LotuStuart]

On 17/03/2024 at 17:18, KaeptnNemo said:

I used a Digital Voltmeter to measure the Injector Voltage, but there was not pulsing any Voltage, neither at the Injector nor at the Connector on the ECU.

and @Sparky

Does a digital voltmeter have a fast enough reaction time to show injector pulsing? Might an analogue meter be better?

Also, were any connections to the relay (positive and output to fuel pump) moved? Is there 12v at the relay power supply pin? although it sounds like the fuel pump is working if there is 3.6 bar at the rail...

[Escape]

I've tested injector leads with a digital voltmeter on several occasions. You might not see 12V, but a decent meter should give a clear indication when voltage is present.

The injectors are powered from the fuel pump relay. It sounds like the fuel pump is able to run to prime the rail, but the relay is unable to supply both the pump and injectors when starting. Possibly due to a bad connection or missing earth. Luckily this is easy to check.

[KaeptnNemo]

That’s what I discovered as well. ECM controls the ground connection of the injectors and they are powered by the fuel pump relay! Interesting point.

Hopefully I find some time tonight for checking that!!!

 

Patrick

 

[KaeptnNemo]

Thanks you all for your help! 
I found it!

I found, that there was no ground at J3C6. Someone gave me a hint, that that wire goes to the top of the gearbox housing. So I removed the heat shrink and…. Tadaaa! Ground wire was torn!