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Just Some Dude in Jersey
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Discussion Starter · #1 · (Edited)
My 2.4 engine with the original Motronic fuel injection never ran particularly smooth since I got all the kinks worked out last Summer. One thing that really pissed me off was that it would bog when I floored it. The engine has, once again, ended up with compression over 200psi(210 across the board) and that meant octane additive, plus we learned that 2.4's are spec'd for 3 atmosphere's of pressure, which is about 44psi. Normal Opel FI uses about 38psi. That helped a little in the power department, but still not right. In recent months it would start and run poorly like one cylinder was reluctant to fire, then it would clear up. Very recently, driving to and from from Carlisle, it would barely let me accelerate without making a missing sound and my air/fuel ratio was at 19+. It shouldn't be more than 16. That means I was running dangerously lean. So I thought it was the bane of all Opels: Vacuum leaks. I redid all the hoses and tightnesses and found a few minor loosenesses and one bad leak at my idle air control valve. Fixed that stuff. The next day I started the car and #4 cylinder didn't seem to be firing and stayed non-functional. It had spark, but only removal of the fuel rail would allow me to check if all the injectors were squirting. So, just in case the Amazon-purchased injectors were cheap junk and one had failed, Charlie and I decided to buy name brand injectors from Rock Auto.

I'm one of the few people who uses the stock all-metal 2.4 fuel rail. 2.4 FI manifolds are too tall to fit under a GT hood, so we're using a 2.2L manifold and throttle, but with the 2.4 Motronic computer, wiring harness, various widgets, and fuel rail. I modded the fuel rail for my returnless fuel injection pump by welding up the return outlet and, since the fuel pump has a built in regulator, I removed and welded up the regulator location on the rail, also. I then, of course, had it chromed. The rail has 2 triangular access plates at each end with rectangular o-rings to seal them. The chroming created substantial ridges and non-flatness where those plates attach and I had to do a bunch of filing and sanding to try to get the rail and plates flat. The rectangular o-rings are unavailable and the ones I had were crusty and flattened and didn't look like they would make a good seal, so I added some copper Permatex sealer just to the OUTER perimeter.

I just removed the fuel rail and injectors. HOLY BEJEESUS! Cylinders 1+2 had sealer in the injectors and at their fuel rail outlets, the pressure tester outlet had sealer in it, more sealer shot out into a bucket after I removed the injectors and turned on the pump, and when I removed the far end plate a giant wad of sealer was looking out at me. It's amazing that the car ran at all. I'm going to have to do a bunch more sanding and filing, so that I don't need to use sealer and the new injectors have arrived, so they'll go in, too.

In the pics below, it looks like a lot of sealer, but it's all actually thinner than a piece of paper. Apparently, my initial filing/sanding of the chroming ridges just flattened the outer perimeter of the fuel rail end caps. They made a good seal. So, when I tightened the 3 screws on each plate the sealer had no place to go except INWARDS. I had only applied a little around the outside and I expected it to squeeze OUTWARDS. I guess it didn't.

UPDATE:
I have just completed filing and sanding of the end caps and the fuel rail ends to remove all of the chroming irregularities. They are now super flat to each other. It took a LONG time. I reassembled with no sealer, just the rubber o-rings. Today I will reinstall the fuel rail with new injectors and see what happens.
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Just Some Dude in Jersey
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Discussion Starter · #7 ·
I put it all back together today and guess what?

No real change. Maybe a little smoother, but the #4 cylinder missing persists. New plugs and diz cap. No change. Swap the #3 + #4 wires. No change. I'm waiting for new plug wires to arrive, but I seriously doubt that's the problem. I see spark when I pull wires. I did bolt tightness and vacuum checks with spray and redid all my hoses and connections and couldn't detect a leak. Compression is excellent at 210psi across the board, so valves aren't the issue.

I know how this is going to play out. There's going to be a vacuum leak under #4 intake port at the manifold where I can't spray anything. It's going to be those darn chroming ridges. The car has one of those 2.4 stainless steel on both sides gaskets. I didn't trust it to seal so I used copper sealer for extra assurance. I'll bet it failed. New squishy Remflex gaskets on order. When the plug wires come tomorrow I'll install them.......and there will be no change and the only remaining thing to do will be to pull the FI manifold, file and sand the crapp out of it, and reinstall with a crushable gasket.
 

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I put it all back together today and guess what?

No real change. Maybe a little smoother, but the #4 cylinder missing persists. New plugs and diz cap. No change. Swap the #3 + #4 wires. No change. I'm waiting for new plug wires to arrive, but I seriously doubt that's the problem. I see spark when I pull wires. I did bolt tightness and vacuum checks with spray and redid all my hoses and connections and couldn't detect a leak. Compression is excellent at 210psi across the board, so valves aren't the issue.

I know how this is going to play out. There's going to be a vacuum leak under #4 intake port at the manifold where I can't spray anything. It's going to be those darn chroming ridges. The car has one of those 2.4 stainless steel on both sides gaskets. I didn't trust it to seal so I used copper sealer for extra assurance. I'll bet it failed. New squishy Remflex gaskets on order. When the plug wires come tomorrow I'll install them.......and there will be no change and the only remaining thing to do will be to pull the FI manifold, file and sand the crapp out of it, and reinstall with a crushable gasket.
How did it not run better without all the sealer stuck in places it shouldnt be?

Karl
 

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It seems highly likely that the injectors themselves are contaminated internally with the sealer.
 

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Just Some Dude in Jersey
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Discussion Starter · #10 ·
New injectors were installed. Fuel rail and line to it were thoroughly flushed and cleaned out, all sealer removed from the system.

The lesson learned is that even with massive amounts of sealer floating around inside the fuel rail, the car still ran just fine for at least 1000 miles before recently.

Does it run better now that all the parts have been replaced or cleaned out? I guess, yes, but I still have that one missing cylinder, so it's hard to make a determination.

And there's a thing when trying to fix a too lean exhaust condition on an FI car that doesn't happen with a carbureted car: After about 30-60 seconds after start up, and detecting the high air-to-fuel ratio, the computer starts adjusting the fuel mix to try to fix it, so you start chasing the problem at the same time as the computer is chasing it. It apparently starts to squirt more fuel to richen the mix. It has no idea where the problem is and the only tools in it's box are how much fuel it can squirt and and changing the spark timing. It's a dumb system and you can plug anything into it to see what it's trying to do, you can only GUESS what it's trying to do.

After I put new spark plugs in it and the missing at #4 persisted, I removed the plug and saw that it was wet, so I know that fuel is being squirted into the cylinder. If I rev the engine pretty high I can hear popping in the exhaust, as though unignited fuel is igniting in the exhaust. Soooo.....there's fuel and I have observed "some" ignition coming from the wire..........

tick....tock...tick....I just went out to the car so that I could pull the plug off #4 and put it on an old plug and ground it to see if I had regular sparking. Before that I thought I would start the car and warm it up, it ran pretty good. I shut down and removed the plug wire from #4 and put a plug in it. I tried to restart. No go. I put the plug back on #4 and it started and ran fine. So now I forget about the spark plug test and decide to watch my AFR and vacuum gauges. Yup, AFR slowly rising from 16.2 to 19, engine running rougher and rougher. So, just on a whim, I decide to lower the fuel pressure from the 3 atmospheres(44psi) I was recently told to do, back down to the "normal" Opel FI pressure of 38. No visible AFR change. I decide to go for a drive to a long time Opel mechanic's shop to pick his brain. As I'm driving the readings from the AFR gauge completely change. Now I'm cruising at 12.6 afr and maybe 13-14 under acceleration. I'm mystified. Huh?


I'm going to have to keep monitoring this situation and maybe do another tweak of the fuel pressure up to 40psi and do some driving. I am soooooo confused about diagnosing FI problems......
 

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You may want to consider having the injectors cleaned ultrasonically.
 

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Just Some Dude in Jersey
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Discussion Starter · #12 ·
New injectors were installed after I cleaned the mess out of the fuel rail. The car is now running properly, although a tad rich based on the AFR reading. I'm going to do some daily drives to see if it is all stable and repeatable and maybe tweak the fuel pressure to get a less rich reading on the AFR. My main concern is that my engine runs healthy, I'm sick and tired of pulling engines.

Here's what I think happened: I developed a bad vac leak where the idle air control valve attaches to my cold air intake system. This may have confused the computer because it wasn't seeing the air come through the air flow meter. The gasket sealer in the fuel rail may have been messing with stuff. Then Charlie saw that the regulator on a 2.4 fuel rail says "3 bar" on it, so I jacked the pressure up to 44psi. I was doing all of this stuff in the garage. Other people have told me that when you do big changes or fixes you need to do some driving for the computer to reset to the new reality. I muddied the water with too many changes expecting instant results, but FI doesn't appear to work that way. With a carb, what you do is what you got, but with FI the computer can do all sorts of things beyond your control. I fixed the vac leak, lowered the fuel pressure to my previous normal, cleaned the funk out of the fuel rail, and installed new injectors, plugs, and diz cap. The car ran smoother but nothing really changed as far as the AFR reading until I went for a drive. Then about 10 minutes into the drive the AFR reading radically changed from lean to slightly rich at 12.6 at cruise and stayed dead steady at that reading. The previous lean condition was constantly fluctuating and changing.

Only time will tell. Drive, drive, drive and see if everything remains stable.
 

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Just Some Dude in Jersey
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Discussion Starter · #14 ·
I haven't, but if the problem returns I'll look into that. I was even thinking of replacing it with a new quality matched and calibrated to each other oxy sensor and gauge that I bought for my project car. I currently have a cheap gauge and some sort of sensor that Charlie set me up with.

Here's a question: Are all oxy sensors pretty much the same as far as the signal they put out or is it super important to use specific sensors for certain cars/engines/set ups?

I wasn't planning on FI for my new car, I just wanted a sensor and a matching gauge, so I bought one. I figured exhaust is exhaust, a sensor is a sensor, and a gauge is a gauge, plus I'm not connecting it to a computer, so I figured it would just give me a basic accurate AFR reading of what's coming out the pipes. But while searching I noticed that the sensors were for all sorts of different engines. I assumed that this meant that they have wiring and harness plus for different FI computers. I currently have a 3 wire oxy sensor, but my new one has 6 wires.

Your thoughts?
 

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O2 sensors can be damaged by use of Sealer (Silicon contamination) and you had sealer on the injector pads at the intake manifold and in the injectors.
Check the tube of your sealer, it should read " O2 sensors safe".
HTH
John
 

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More Opels than sense
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Here's a question: Are all oxy sensors pretty much the same as far as the signal they put out or is it super important to use specific sensors for certain cars/engines/set ups?

Your thoughts?
I'm running the Motronic setup on my 2.4's (and 3.6 Monza) and I use the Bosch universal 3-wire 13913 sensor. Readily available and cheap, although you do need to cut the plug off the new sensor and solder it to the connector for your old sensor.

Nick
 

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Just Some Dude in Jersey
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Discussion Starter · #17 ·
I bought this type because it had the same part number and the connector was the same as my harness:


So, an update on this issue I was having. The primary issue of the engine behaving as though it had one partially missing cylinder and an extremely lean AFR reading, for vacuum, spark, or fuel issues, seems to have been mostly a loose fuel injector connector on #4. Or loose fitting connectors at all my injectors generally. There's no one thing you could pin the whole problem on. But, a drive to a car show on Monday revealed an annoying problem: #2 fuel injector wire plug would keep popping off. The harness is brand new, the injectors are brand new, the plug clicks in place nicely and you can't pull it off, but 10 miles down the road and I've got a missing cylinder. The plug came loose. It popped off 3 times during the one hour's worth of driving. #2 cylinder? It was #4 that was showing evidence of not working properly before! WTF? I bought special high temperature wire ties and have wired tied all 4 injector plugs so that they can't pop off. The car has behaved well during the handful of 3 mile test drives around the river near my house.

Let's recap: After almost 6 months of tinkering, I got the fuel injection to run decently, I guess, around the middle of last year. It didn't get driven much due to Covid and almost no car shows to go to, then there was Winter hibernation, then the usual frantic scrambling to get our cars running after Winter in time for Carlisle. Did I have it running perfect? I don't know, I have no reference point of having seen a perfect, normal 2.4, running. It seemed pretty good to me, but maybe there were little issues of running perfection that I didn't have. I'm used to the way my previous side draft set up on a 2.5 sounded, which was gnarly, nasty, and ferocious. The FI on the replacement 2.4 seemed to run cleaner than the SSD'd 2.5 engine, but also lacked the balls and ferocity and I could never floor this engine without it sort of bogging. After all the stuff I recently did, it doesn't bog anymore and is now pretty close to how the side draft 2.5 engine performed and I can now floor it and get good response.

The primary culprit that led me on this wild goose chase was my horrible AFR reading. I have, at times, gotten that AFR reading down to a more acceptable 13-15, but then a couple of miles later it's back to 17-19. Absolutely no change to how the engine ran, whether the AFR was saying 13 or 20. Since I've replaced or redone almost everything and my vacuum gauge says that I'm at a nice strong 17Hg, I'm ruling out vacuum leaks, so that leaves one item that I haven't replaced yet: The oxy sensor. I'm waiting for several of those to come in the mail. My hope is that various bad running conditions have partially fouled my O2 sensor and that maybe installing a new one will get the AFR to read consistently.

Here are the problems I found and fixed and the parts I replaced:

1) Hideously clogged with sealer fuel rail and injectors - Cleaned out and removed all the sealer from the fuel rail and installed new injectors.
2) Very loose IAC hose connection before the throttle - Put the IAC hose on it's intended location on the throttle body and replaced the modded, leaky, cold air intake elbow with a new unmolested one.
3) Injector plugs that want to keep working loose - Wire tied them in place and tied down the wires leading to them to eliminate any potential wiggling.
4) Tightened or redid various vacuum manifold hoses and checked their air tightness
5) Replaced my vacuum gauge and hose with a new one that used a much bigger clear hose and then replaced that clear hose with a much longer lasting rubber vacuum hose. The previous gauge's tiny clear hose had dried out and cracked off, creating a small vacuum leak.

I installed:
New plugs
New plug wires
New diz cap
New injectors
New intake elbow
New vac gauge with a big sturdy hose
I added octane booster after learning that my 210psi compression across the board really calls for race gas
Still waiting to install a new O2 sensor.

Each of the above things created a barely discernable improvement in the car's running. The octane booster and wire tying the injector plugs had the greatest effect.
 
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