Manta efi problem

[moodoo]

Hello everyone - I'm new here..!
I'd like to firstly say thanks to all for the excellent information that these forums contain. I've spent a couple of days trawling through, and have found loads of good stuff.

Now, onto my problem...
I have a 1972 Manta, which has been fitted, by a previous owner, with LE-jetronic injection. I've had the car for a few months, and has run perfectly, until now...

I had noticed the last couple of times I had the Manta out that she was on 2 or 3 cylinders at first, but it'd clear and run fine after a minute or two. Monday night she wouldn't start...it would almost start, or start, but run really bad on 2 or 3 cyls, only for a couple of seconds, and die.

The plugs smelled strongly of fuel, and they're quite black (they're new plugs, less than 100 miles). Taking a plug out at a time and cranking, I can see that each plug is sparking OK. (I changed back to the old plugs I had changed out anyway, which had been a nice 'biscuit' colour, but these ended up the same black after a few attempts at starting.)

I started with the air bypass valve. Took the hoses off, and used a light and a mirror, and with the engine cold it is open a bit. I have no idea how open it should be though...?
Thought that it was OK once it was open a bit, so connected its hoses again.
Disconnected cold start injector to make sure it wasn't turfing in a load of fuel, but still the same problem with start/idle.
Next disconnected the air bypass hose at the manifold entry port and started the engine. Hey presto she started fine, and revd herself cleanly all the way to 3k rpm, running perfectly cleanly. Connected the bypass valve hose again, and she died. Repeated this a couple of times.

So...I take from this that the problem isn't on the coil/distributor/plug lead side, since she runs cleanly once she gets going.
It also looks like for sure its a mixture problem at start/cold idle. I can't figure out why the engine idles at 3k with the air bypass line disconnected though? OK, its getting more air, but since the airflow meter isn't opening, how are the injectors knowing to add enough fuel to run at the high rpm? I presume even with extra air there isn't enough fuel put in in idle condition to run steadily at 3k? Didn't run her like this for very long, in case I had a very weak mixture which was about to melt everything...

Does this sound like the air bypass valve is at fault, or is disconnecting the hosing just masking something else..? Is there another way to check using a voltmeter etc., if the bypass valve is OK?

Sorry for the longwinded post, but I figured better too much info than not enough..

Thanks in advance,
Fin

[DennisGardiner]

First welcome to the group.

Luckily Opel's LE injection is super simple. A good tech manual with 'diagnostic flow-charts' will be your best friend. So getting one will be paramount.

BTW,... when you disconnected the cold-start injector. (and it made no difference), did you
A) only unplug the wire connector
or
B) disconnect the fuel line.

Why? Because if you only disconnected the wire connector, (leaving the fuel hose attached) the injector could still have been leaking fuel.
__

Regarding fouling plugs, (stuff that's happened to me)

1) clogged air filter (caused extremely poor mileage and plugs were black)

2) slightly corroded cap wire sockets and wires (from moisture)
-caused a misfire & the plugs to foul inside of 2 miles-

3) weak ignition coil (spark looked okay, but was not delivering enough power)

4) excessive fuel pressure
- defective fuel pressure regulator
- restricted fuel return line

You should have around:
- 32-36 psi @ idle (high engine vacuum)
- 42-44 psi @ full throttle (low to vacuum or disconnected vacuum hose @ regulator)

5) improperly spraying injector/s

I'd start here. But do not forget to give everything a quick check & once over. Sometimes a connector needs cleaning or tightening. Fuel filter need replacing, etc.

Don't assume "It's Okay", you'll get in trouble every time.
__

BTW, disconnecting the vacuum hose to the air by-pass valve (for cold engine operation) is supposed to increase the idle speed.

This valve (cold) should be almost wide open, and (hot) mostly to completely closed off. Also this valve has an internal heater strip that warms as soon as you turn on the key.

Good Luck.

[David McCollam]

The thermotime switch is most likely out on the FI. This temperature sensor enriches the fuel mixture at cold start. It tells the cold start injector to inject excess fuel. If the thermotime switch is bad/loose, the computer will signal the cold start injector to inject fuel as if the engine were continually cold. By removing the idle air bypass hose, you introduce a ton of air to support the rich mixture at the 3000 rpm idle.

Try pulling the thermotime switch and jumping the connection with a short piece of insulated wire. This will simulate a warm engine and let you know if the thermotime switch is indeed the problem. The thermotime switch is the brown connector coming in at an angle into the thermostat housing, below the idle air bypass valve.

Good luck,

Dave

[moodoo]

Thanks a lot guys...more of the expert help I've seen on this forum! Big thumbs up.

Dennis - thanks for the tips:
1) Air filter is brand new...less than 50 miles.
3) I believe the coil is OK, since it runs fine at 3k rpm, and this evening I was able to get her to run at a nice idle and up to 4k once the engine got warm.

I removed the cold start valve (although not until after the engine was warm...have to wait until tomorrow to have the engine cold to try it), and on starting its not leaking.

Fuel pressure I still need to check.

Before I got to my PC this evening, I had a tinker in the garage...

The resistance at the bypass valve is 46 ohms. Theres a link somewhere on the forum to a really detailed Porsche 912 L-Jetronic manual...I read in there that the resistance should be 30ohm. Anyone care to guess if that 30ohm is still valid for Jetronic LE? In that case would my 46ohm indicate a problem?

Also, on further inspection, the bypass valve looks quite closed to me, even when the engine is stone cold. Looking down the barrell of the valve, all that was open was a small 'triangle'. Using a fine screwdriver, I was able to open the valve manually, quite a lot more...but I don't know how much it should be open at cold? Even tried putting it in the freezer for a while to see if it would open more, but it didn't. The valve does close more when the engine is warm alright.

With engine cold, I left the bypass line connected to the manifold, and disconnected it on the intake side of the bypass valve. Car started and idled normally. Reconnected the line, car wouldn't start.

I was able to get the car idling and running OK once it was warm, past the point where the bypass valve had closed off.

David - thanks for the tips on the thermotime switch...I will try something tomorrow or at the weekend.

If anyone can tell me what ohms they got on their bypass valve, or how 'open' is 'open' when cold, that'd be great.

Updates to follow..!

[DennisGardiner]

Originally Posted by moodoo The resistance at the bypass valve is 46 ohms. Theres a link somewhere on the forum to a really detailed Porsche 912 L-Jetronic manual...I read in there that the resistance should be 30ohm. Anyone care to guess if that 30ohm is still valid for Jetronic LE? In that case would my 46ohm indicate a problem?

The thermo time switch on my 2.0L EFI reads 33 ohms cold.

Originally Posted by moodoo Also, on further inspection, the bypass valve looks quite closed to me, even when the engine is stone cold. Looking down the barrell of the valve, all that was open was a small 'triangle'. Using a fine screwdriver, I was able to open the valve manually, quite a lot more...but I don't know how much it should be open at cold? Even tried putting it in the freezer for a while to see if it would open more, but it didn't. The valve does close more when the engine is warm alright.

Good, as long as the Auxiliary Air Valve opens and closes.
BTW, these valves can be altered from their factory set setting,... if you so dare.

Another item to check, is the temperature sender for the computer. With coolant at 176 F the reading should be less than 350 ohms.

[Aardvaark]

The aux air valve can also come out of adjustment if the stationary end of the bi-metallic spring which is retained in the wire connector and held in the aux air valves body comes loose. I've seen two type of these Bosch AAV's.
One type is held together at the connector end with the friction of being
squeezed and the other is held from turning with a small cross pin.

The former type can slip and cause the cold air port to go bad and also not open correctly when heated up. I bought a used one from OGTS because I though mine of the first kind was shot. But after replacing it with the used one, which is of the pinned variety, I spotted the problem with the old one and fixed it for a spare.

You might want to take a look at yours since our symptoms are/were very similar.

[moodoo]

Originally Posted by DennisGardiner The thermo time switch on my 2.0L EFI reads 33 ohms cold.

Thanks a lot for the reading. Any idea what your air bypass valve reads/should read? My bypass valve reads 46ohms, I didn't measure the thermo-time switch yet...

Originally Posted by Aardvaark The aux air valve can also come out of adjustment if the stationary end of the bi-metallic spring which is retained in the wire connector and held in the aux air valves body comes loose. I've seen two type of these Bosch AAV's. One type is held together at the connector end with the friction of being squeezed and the other is held from turning with a small cross pin. The former type can slip and cause the cold air port to go bad and also not open correctly when heated up.

Not sure what type mine is, the 2 halves of the valve seem to be held together with 3 small pins, and theres also a nut screwed to a stud on the back...I guess this is the pivot?
Does the aux air valve not close when heated up?

[Aardvaark]

Originally Posted by moodoo Not sure what type mine is, the 2 halves of the valve seem to be held together with 3 small pins, and theres also a nut screwed to a stud on the back...I guess this is the pivot? Does the aux air valve not close when heated up?

I'm referring to the connector end (rear of engine end) where the plastic piece that holds the internal spring stationary and also is the electrical connector socket can slip on the non-pinned type.

Yes, the valve closes when heated up by the internal heating element and engine heat. But if the electrical connector end slips and rotoates, the internal spring no longer operates the valve disc to shut it and your engine can run very lean when warmed up.
Try grabbing the electrical connector socket piece and twisting it gentally.
If it moves, it has come loose.
My hunch is that many repairable aux air valves have been tossed. I almost did.

[moodoo]

Update...
Tried moving the electrical connector on the bypass valve...doesn't budge, so I guess its ok?

With engine cold I..
..Cleaned up fouled plugs
..measured 36 ohms at thermoswitch
..measured 230Kohms(!) at temp sensor
..removed cold start injector
..started engine, cold start injector fired for 2 or 3 seconds then stopped. Engine just almost started. Cranked again, engine didn't start, but cold start valve didn't fire this time. Screwed cold start valve back in, cranked engine, and she started. Quite rough,with a very low idle speed, but she managed to stay going. Seemed like it was on 3 cylinders some of the time. As the engine got hotter the idle speed went up, and idle improved.
(Now measured 74ohms at thermoswitch, and 1.6Kohm at temp sensor.)

Allowed her to idle another while, car ran cleanly, took it for a drive, no problems.

So its certainly a cold start mixture problem.

What I think happened is that at first, with the cold start valve removed, she didn't start becuase it was too lean, as there was a great big opening in the intake manifold, and there was no extra cold-start fuel. Then, it seems like the cold start valve wasn't firing any more (thermo switch up to temp?), so once I re-installed the injector, she was effectively starting from cold, but without any 'help' from the cold start valve. This left the mixture slightly leaner, and so she started...

I'm still at a loss as to why this might be happening. My resistance measurements on the thermoswitch weren't what I was expecting, but the cold start injector seems to be operating correctly, so I guess its OK...

Somehow I still think its the air bypass valve not letting enough air in when cold. What else would cause the mixture to be too rich, only on cold start up..?

[DennisGardiner]

Originally Posted by moodoo Thanks a lot for the reading. Any idea what your air bypass valve reads/should read? My bypass valve reads 46ohms, I didn't measure the thermo-time switch yet...

Same, 46 ohms

Originally Posted by moodoo Not sure what type mine is, the 2 halves of the valve seem to be held together with 3 small pins, and theres also a nut screwed to a stud on the back...I guess this is the pivot? Does the aux air valve not close when heated up?

Yup, the nut is used to dial in the 'amount' of air to bypass when the engine is cold. But, I'd assume it's still properly set from the factory.

[Aardvaark]

With everything back together, it might be time to hold the throttle plate open a bit before cold starting it to let it get air it may be missing from a bad Aux Air Valve binding or having a bad spring. If placing a couple of dimes under the throttle stop allows the engine to start and idle faster then you might try cleaning the aux air valve or replacing it if cleaning doesn't help.
That was how I diagnosed mine as bad and bought the used one from Dennis
to start with.

[Paul]

Originally Posted by moodoo she didn't start becuase it was too lean, as there was a great big opening in the intake manifold, I'm still at a loss as to why this might be happening.

Did I read this right??? Are you saying that you removed the entire cold start injector and left an open hole in the manifold where it had been??? If so, that WAS a big problem, since unmetered air was entering here and not through the air flow meter. I'm not suprised it wouldn't run. This hole must be blocked. I would have disconnedted and bolcked the fuel line instead.

FWIW, The thermo time switch operates much like its name implys.... as it only operates the cold start valve for a limited amount of time, usually for just a few seconds.

[Aardvaark]

Originally Posted by Paul Did I read this right??? Are you saying that you removed the entire cold start injector and left an open hole in the manifold where it had been??? If so, that WAS a big problem, since unmetered air was entering here and not through the air flow meter. I'm not suprised it wouldn't run. This hole must be blocked. I would have disconnedted and bolcked the fuel line instead.

Yes he is saying that, but was simply checking the cold start injector for
brief spray operation, not expecting the engine to start. He did it correctly.

[wrench459]

I just cant help but thinking the AFM flap is sticking half way open some times.

[lowkey]

Try another coil.

Seroiusly, they'll fool ya, and drive ya crazy on problems like this.

"Back in the Day," working at the dealer, the coil caused more strange problems like this than anything else.

It wouldn't hurt to try.

[moodoo]

Originally Posted by Aardvaark With everything back together, it might be time to hold the throttle plate open a bit before cold starting it to let it get air it may be missing from a bad Aux Air Valve binding or having a bad spring. If placing a couple of dimes under the throttle stop allows the engine to start and idle faster then you might try cleaning the aux air valve or replacing it if cleaning doesn't help. That was how I diagnosed mine as bad and bought the used one from Dennis to start with.

Yep, will try this...might use some euro coins rather than dimes though...

Originally Posted by wrench459 I just cant help but thinking the AFM flap is sticking half way open some times.

I took the airbox off and moved it back and forth a few times, it seemed to move freely enough...

Originally Posted by lowkey Try another coil. It wouldn't hurt to try.

No it wouldn't. but unfortunately I don't know anyone else with a car I could try bits from, so any bits I want to try, I'll have to buy. I don't mind doing it, but just want to be reasonably sure I'm buying bits I need. Having a spare coil is probably a good idea anyway I guess.

somebody suggested to me that the injector(s) might be dirty, not sealing properly, and leaking fuel into the cylinders overnight...which sounds like it could cause my problem. Easy enough to check I guess, remove injectors and leave sitting over a container or something overnight. Anyone else had this problem?

Thanks for all the input guys! As I said, with not knowing anyone else with a classic, it means the internet is my support for stuff like this.

[lowkey]

Not all fuel injection problems are the same. The things you're wanting to do, are the kind of things that on a flowchart, would be for intermittent, problems at speed.

Dirty injectors won't cause the kind of problem you're having.

A coil is cheap, and takes minutes to change, and probably needs replacing anyway.

That's just my thoughts.

But I come from the try the cheap, easy to replace stuff first, school of thought.

[moodoo]

I found tonight that the idle contact of the throttle switch wasn't being made at idle. Fixed that, but it doesn't seem to have made any difference. I read somewhere that this idle contact isn't actually used. Is it?

Something I thought...seeing as the resistance of the temperature sensor goes down as the engine heats up..if I jumpered the plug connection with the engine cold, would this trick the engine into thinking it was warm, to see if the temp sensor is at fault? Would this do any harm to the ECU, seeing as my jumper will have virtually 0ohm resistance, but even hot the temp sensor would have a few hundred ohms?

Yeh, you're right...I'm probably at the stage of buying a few parts to try and replace them one by one. Changing the coil and the air bypass valve will be top of the list I think.

During all this I've also found a number of plugs with broken housings and/or missing retaining pins - the cold start injector and 2 main injectors. Also found a cut in the insulation of the wire going to the temperature sensor. So certainly a few things to fix, although I don't think these are causing the problem.

[moodoo]

Folks, would anyone be kind enough to take a picture down the barrell of a known good air bypass valve when cold?

Tonight I made up some resistor leads, so that I could mimic a cold and hot engine. I made them up to the same resistances that I had measured at the temp sensor under different engine temps.

'Cold' resistor in instead of temp sensor...car is lumpy and idles very poorly.
'Hot' resistor in instead of temp sensor...car idles and revs perfectly.
With cold resistor in, she's putting in too much fuel for the air available. I want to try a new bypass valve, but I'd love to see how open they should be when cold. I've only seen mine, which is open somewhat when cold, so I've no reference point...
Thanks!

[dallasmanta]

I took a picture for you facing the sun so you can see the sliver of an opening in the air bypass valve. see below

Paraphrasing from the bosch L-Tronic book. the Aux air device is used to provide additional air during cold startup only to prevent wet plugs and give the engine more torque to overcome the internal frictional resistance for a cold engine. The plate closes completely once the coolant temp reaches 60 to 70C. It will not engage above this temp.

The Thermo time switch closes or opens the electrical circut leading to the cold start valve depending on the engine coolant temp. The function of this switch is to limit the time the cold start injector fires into the manifold ( 0-15C temp and between 5-20 seconds depending on the engine).

The Temperature sensor on the other hand will enrich the fuel requirements 2-3 times of a warm engine. This is what someone earlier in the post suggested you test by unplugging the sensor and jumper the connector to simulate a warm engine. You need to do this and your car should start a lot better.

Having read everything in this post. I suspect this it the main problem you are facing.

If your morning air temps are in 40-50F range and you start the engine does the engine idle up a bit. If it does then the Aux air device would not be suspect. I have given up trying to replace this part on my 75 Manta as I can compensate for it using air bypass nut on the manifold to idle up the engine speed and or adjusting the air flow meter to change the air fuel mixture. Smelling the exhaust to avoid unburnt petrol fumes is the old school way to set it . Hope this helps Ron

[moodoo]

Thanks very much for the pic DallasManta.
I don't know if the opening is much bigger than what I see, but it certainly is a different 'shape'. Hmm...

I did exactly what had been suggested, by using a 'hot' resistor (about 400ohms I think) across the the temp sensor when the engine was cold, the engine ran fine, as it thought it was hot, so it was putting less fuel in than it would have under normal cold start. When I put the 'cold' resistor in (14k ohms), she was lumpy and running badly again.

Have had a couple of people say that their cold temp sensor reads around 2k ohms (mine reads 230k...but I had read somewhere that its normally 12-14k, don't know if thats right?), so perhaps my temp sensor is bad, and is telling the engine to put enough fuel in for an artic cold start...!

Will need to start looking for a temp sensor I think...

[dallasmanta]

The temp sensor is a tricky one to test as it is based on coolant temp. What you tested was at both ends of the range. The actual operation is liner in function and you are not testing it in warm up range at all with the shunts you have built. You are testing it both extreme ends.

This sensor unit is responsible for poor miles per gallon in most FI opel engines because they always run rich. This sensor unit is interchangeable with BMW 3.O SI, CSI, 530I, 630I, Renault 17TS from 75 to 77years. The part number is 0 280 130 023. It may also cross over to the Triumph TR8 and the Jaguar early FI system. Most of those engines are bigger in displacemet and use the same sensor. Now you know why the plugs are so wet. Living in in the Ils you should not have much trouble finding this sensor. Ron

[Aardvaark]

Napa has them for our Opels, but not Bosch:
NAPA Online PartsPRO SE

[moodoo]

Just a quick update on this, for the sake of anyone else who might encounter the same problem. I bought a new temp sensor, not Bosch, but a generic one (thanks to Ron for the Bosch number though!). Problem fixed! Car now starts and idles nicely when cold.

Thanks to all for taking the time to help me out, much appreciated!