Checks on '75 Factory FI Operation
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Thread: Checks on '75 Factory FI Operation

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    Opel Rallier since 1977
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    Checks on '75 Factory FI Operation

    Been getting our '75 1900 FI system up an running; it will sputter upon cranking on the squirt of fuel from the cold start injectors, but not catch and run.
    - Fuel pressure is a bit high but moves to 43 psi on the gauge when sputtering; fuel stays on
    - Injectors pulses do not appear to be come from the ECU when checked with an oscilloscope so this is the problem. I have probed inside the ECU and no pulses into the final drive transistor (that switches the injectors) are present.

    I have one coming from Soybean but I want to make sure it is not something else I am missing as an input to the ECU. The tach signal is there, but it is not as strong as I would expect from looking at a points system. (But, I have never had an o'scope on an Opel e-coil system so really do not know what it should look like; I am just referencing a Mopar system, which puts out pulses of about 200V peak.) Condensor is new and points look good. I may swap points.

    I have a resistor in the harness in place of the coolant temp sensor (which is shot) to simulate about 80F.

    The ECU is putting out what seems to be a sutiable reference signal to the MAF sensor and the MAF sensor is returning a signal that would be in the normal range when it swings open when trying to start. Throttle position switches are making contact.

    Dual relay has been cleaned and a new one also put in place.

    So what other signals could be missing that could inhibit the ECU from pulsing? Tnx!

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    Senior Member dallasmanta's Avatar
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    check your grounds

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    Opel Rallier since 1977
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    Thanks very much for your suggestion! Yes, those are good; I went via the manual and they are all there and going to the right spots. Turns out the ECU is probably bad; I got a spare from Soybean, and that made the injectors operate. I have not put the o'scope on it again, but it is at least running past the cold start injection squirt. We found the alternator/regulator harness hacked into, so someone may have tried 'fixing' the alternator with the foolish tactic of putting 12v directly on the field terminal, shot the alternator output voltage through the roof, and blew the ECU out.

    We have progressed to get the pressure right with a proper pressure regulator (from Herko in Miami), and now have found that the MAF is not moving the potentiometer wiper to the right spot when idling. I can manually move it there, and and thus adjust the idle mixture to idle properly. And the spot where I hold the wiper is identical to where Charles Goins' YouTube videos 4 & 5 show the MAF airflow vane to move the wiper at idle. This is not just due to the air bypass screw setting; it is waaay off from where it should be. So it looks like either a PO substituted another MAF and put the original Opel MAF cover on it, or they really radically tightened the clock spring setting trying to lean out the mixture a ton.... like moving it almost a full turn! We can see where this spring holder has been moved before.

    Here is some info that I could use: What is the spec on the rotating force needed to move the vane/wiper off of the no-airflow stop when pushing on the little tab at the back of the clamp screw? (I ought to post a pix.) I have found a certain BMW MAF spec of 55-60 grams; this one takes 220 grams to get it to start to move! No wonder it does not open (or hardly at all) at idle airflow.

    So we are getting this sorted out; over half the FI components are wrong, mucked-up, or broken: temp sensor, ECU, pressure regulator, MAF and auxiliary air valve so far! I can't tell if this is a really bad hack job or there was some performance objective in mind. The injectors were the original 104's so the latter seems like a forlorn idea.

    Again, thanks!
    Last edited by Manta Rallier; 2 Weeks Ago at 02:17 PM.
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    Opel Rallier since 1977
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    Just an update on this MAF-AFM spring setting that I mentioned above for anyone with this system:

    That reference to setting the just-off-the-stop tension on the back of the pinch bolt of the wiper of 5-60 grams. was for an AFM for a K100 BMW 1000CC bike; so a smaller engine but a starting point. I moved ours 34 teeth to get there it was well over 200 grams to start. This AM in testing it was very close and THEN I spotted a depression in the gear plastic gear teeth 4 teeth away (lighter tension) and moved it there...Bingo, all good! I think that was where the original setting was; a PO had moved this danged thing 38 teeth (out of 54 teeth for a full gear wheel rotation)!!! We think some one was messing with it, and let the spring go and just whacked it all out trying to get it back.

    So, if you have one of these and want to get the spring setting close to factory (IF the original spring setting has been lost, or you just have no idea where it is at), I'd start with 50 grams tension at that point. That is 50 grams on a tangent through the little tab behind the pinch bolt. EDIT TO UPDATE: I got a 2nd AFM and the spring pressure was set so that the torque off-the-stop was over 200 grams. Sooo, the above setting of 50-60 grams may well not be factory for these '75 Opels. But both the units I have have been opened in the past by others so I cannot say 100% either way.

    At least it will idle now, with the AFM wiper moving to about the right spot. Now to get the alternator fixed so we can have full voltage to the injectors. We are finding that whatever system the PO touched, we have to go back and fix... a LOT! Brakes, alternator, FI, instruments are on the mucked up list so far LOL.....
    Last edited by Manta Rallier; 1 Week Ago at 02:39 PM.
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    Member Gordy's Avatar
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    I replaced everything on my 75 Manta's efi when I went thru it a few years ago. Have all the sensors, injectors, relays etc I took off. PM me if there are certain items that you still need.

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    PM sent, Gordy; many thanks!

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    Opel Rallier since 1977
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    Well now for a new question:

    Has anyone ever measured a cam out of a '75 FI engine? Ours has the 19E marking on the block and X19A on the head. The lift is as low as a standard early 70's cam, and maybe even a bit lower like a 15N/17N cam. I got .245" lobe lift on 3 of 4 intakes and on the one exhaust lobe checked, with a dial indicator. I found info that the 19E cam was a higher lift cam (see link below). I don't think this one is worn all THAT much. Maybe this has a non-'75 head?

    Just trying to figure out why this engine does not pull the intake charge that it seems like it should; the AFM spring has to be set waaaay soft to get the system to idle, and even softer to get the engine to rev without a lean misfire. Maybe this is why there was a higher pressure fuel pressure regulator in the car.

    Here is that link on cams..... What I don't know is if the 19E listed here was for this '75 model year in the US or is perhaps a different Euro model??? Since this table does not list the 19US engine, perhaps this info is only for Europe and not the US.
    https://tekenaar.opelgt.com/Opel%20C...tcamspecs.html

    Thanks, Mark B.

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    Is there a letter stamped at the end of the cam, like this:

    The Euro spec 19E cam is a solid lifter cam that was used in the 105hp and 115hp Kadett C GT/E and the 105hp Manta A GT/E. The US spec 19E seems like a Euro 75hp 19N low compression engine with an L -Jetronic FI-system, except that it has a hydraulic cam(Euro 19N has a solid cam).
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    I will have to check. What does the 'B' signify? This car has been in the US since new, and definitely has the low compression pistons.

    What I have is hydraulic and the table I linked says the 19E is hydraulic, not mechanical.
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    Project 1450 supporter... Site Supporter RallyBob's Avatar
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    As far as I have ever been able to tell, the 1975 US spec cams were the same as all the other hydraulic cams in the US.

    Given that emissions were a bigger concern than power here, that does not surprise me.

    Also consider that a Euro 1.9E made 105 PS but the US version made 81 SAE NET HP.

    Also consider that a US-spec 1974 Opel was rated at 75 HP. The 1975 was rated at just 6 HP higher. It was partially due to the EFI intake’s higher airflow, and due to the 1975 ‘Sprint’ exhaust manifold’s higher flow.

    If the cam was bigger/better, the power would have been higher, and likely at a higher rpm.
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    That info is appreciated, Bob. I will ignore that other table, and rule the cam out now as anything but normal for this engine. Cam timing is not far off... looks like a few degrees retarded, based on the sprocket position relative to the sprocket support notch at TDC......i.e., what you would expect for a worn/stretched chain.

    We actually got the somewhat cleaned and de-rusted fuel tank back in today (boy, was that a royal mess with 5-6 year old fuel and moisture!), and the car on the ground and drove it around this evening, and it felt pretty good. The AFM seemed a bit rich at idle (by smell & plugs, no AFR gauge on the car yet) so I adjusted it it back and forth a bit and got it leaner at idle and still has good throttle response, and is not missing/bucking lean. I'll know more after more driving. It is just perplexing that the AFM clockwork spring had to be lightened up about 48-49 teeth (out of 54 teeth in a full turn) to get the AFM to run right. The torque needed to move the AFM wiper off-the-stop is pretty much 0 now.
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    Quote Originally Posted by Manta Rallier View Post
    I will have to check. What does the 'B' signify? This car has been in the US since new, and definitely has the low compression pistons.

    What I have is hydraulic and the table I linked says the 19E is hydraulic, not mechanical.
    The B doesn't mean anything special, it's just a "name" for the cam. It was used in the 25S/H/E, 28S/SC, and 28H/HC engines, except the D-Jetronic equipped -70 to -71 25E and -78 and up 28H.
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    Project 1450 supporter... Site Supporter RallyBob's Avatar
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    Quote Originally Posted by Manta Rallier View Post
    Cam timing is not far off... looks like a few degrees retarded, based on the sprocket position relative to the sprocket support notch at TDC......i.e., what you would expect for a worn/stretched chain.
    The cam is ground 1 degree retarded in stock form. So with a stretched out chain you’d probably see 2 - 3 degrees of cam timing retard.

    Years ago C & R sold 90% of their cams with 3 degrees of advance ground in to compensate for this.
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    Yes, the ground-in cam advance thing is pretty common nowadays all over.

    BTW, I found a brand new exhaust head pie leaning in the back corner of the garage complete with the C&R shipping label... I think I bought this over 25 years ago.... an antique! LOL

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    Quote Originally Posted by RallyBob View Post
    As far as I have ever been able to tell, the 1975 US spec cams were the same as all the other hydraulic cams in the US.

    Given that emissions were a bigger concern than power here, that does not surprise me.

    Also consider that a Euro 1.9E made 105 PS but the US version made 81 SAE NET HP.

    Also consider that a US-spec 1974 Opel was rated at 75 HP. The 1975 was rated at just 6 HP higher. It was partially due to the EFI intake’s higher airflow, and due to the 1975 ‘Sprint’ exhaust manifold’s higher flow.

    If the cam was bigger/better, the power would have been higher, and likely at a higher rpm.
    Well, the 7.6 vs 9.2 compression ratio may have had something to do with that, too.

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    Project 1450 supporter... Site Supporter RallyBob's Avatar
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    Quote Originally Posted by 72Rallye View Post
    Well, the 7.6 vs 9.2 compression ratio may have had something to do with that, too.
    It helps, but not as much as you might think.

    US 1971-1975 engines were rated at 7.6:1 compression. They actually measure out to be closer to 7.13:1.

    Early US engines (and Euro versions) were rated at an even 9:1 compression, but Opel was optimistic here too, as they measure out at around 8.38:1 true compression.

    That’s a difference of 1.25 compression points.

    Even if you’re feeling generous and you say that 1 point of compression is worth a 4% power increase, we’re only looking at a 3.75 hp bump from 75 hp up to 78.75 hp.

    Not enough to make up all the difference.
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    The added compression helps a LOT in the low and mid_RPM torque numbers. That is the deceiving part about the HP increase; it may rease the PEAK HP by 4% or so, which occurs at the high RPM end, but it raises the low RPM torque numbers quite a bit more than that few %. There is a reason you can feel it in the seat of your pants.....Going from 7.6 to 9 is quite a performance difference unless all you care about is drag racing or dyno HP numbers.

    Interesting above on the actual compression ratio numbers..... I have worked out ACTUAL Mopar small block compression using the proper dimensions, etc., and in this same era, their real production engine CR numbers are typically .5 to .75 point lower than the published numbers. You could only reach their published numbers with the very smallest possible head chambers, ones way to on the lowest end of the variations, and maybe even just when they have been milled some, like to meet NHRA chamber size minimums So it looks everyone was playing the same game!.

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