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grannyknot

Trouble shooting

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I'm on page 33 of the fuel injection bible, http://www.atlanticz.ca/zclub/techtips/efisystem/280zfuelinjectionbook.pdf

No. 5  Power relay control unit injector test, it says to disconnect and reconnect the ignition lead wire several times while listening to each injector, so what do they consider the ignition lead wire? The pos side of the coil, center lead of the coil?

I have a no start situation so working my way through the steps.

Thanks

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Ignore this post.

Edited by SteveJ

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Ignore this. It got to the wrong thread

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7 hours ago, grannyknot said:

I'm on page 33 of the fuel injection bible, http://www.atlanticz.ca/zclub/techtips/efisystem/280zfuelinjectionbook.pdf

No. 5  Power relay control unit injector test, it says to disconnect and reconnect the ignition lead wire several times while listening to each injector, so what do they consider the ignition lead wire? The pos side of the coil, center lead of the coil?

Man... That was confusing, but I think I figured it out.

First, the simple (Obvious) answer... If you look at the prior page (32) of the FI bible, they show you how to locate the "ignition lead wire" and there is even a picture to show you what they are talking about. What they want you to do is disconnect and re-connect the wire that goes to pin 1 of the ECU, and the way they suggest to do that is to make and break the single wire connector under the dash next to your fuel injection relay above the driver's knee.

But here's the rub..... You don't HAVE that single wire connector. You see, what happened is that the FI Bible was written in 1975, and hence, it referenced the 75 design and documentation, and in 1975 (and 76) there WAS a single wire connector there.

But by the time they got to your (and mine) 77, they did away with that separate single wire connector and ran all those wires (including the input trigger signal) through the same connector that mates to the under dash harness. You do not have a single pin connector that funnels the ignition lead signal from the firewall under-dash harness to the FI system. That whole part of the FI bible does not easily apply to 77.

All that said... What they want you to do is make and break the connection to pin 1 of the ECU (which is the ignition input signal). Easier to do in 75 or 76 than in 77.

So here's what I would do instead:

Pull the center high voltage wire out of the distributor and place it close to a good ground like the intake manifold or strut tower nut.
Leave the other end of that coil wire connected to the coil as normal.
Turn the key ON.
Connect one side of a piece of test wire to ground.
Ground and unground the negative side of the coil a bunch of times.

You should get a spark from the coil wire to ground every time you unground the coil negative, and you should get an injector click on every third.

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Glad to help. Hope you figure out what's going on.

And thanks for highlighting a year related issue with the FI Bible. I never looked into it that deep and didn't know there were surprises like that in there. That could potentially save some other 77-78 owners major confusion in the future now that we're aware of that shortcoming.

FYI, there is a later version of the FI Bible from 1980. It suggests grounding the negative side of the coil and doesn't talk about that single wire connector at all. Despite that, I still like the earlier version better than the 1980 version.

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I did a lot of testing today and most of it had good results but some were strange, I'll check everything tomorrow and do those tests again just to be sure I have hard numbers.

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So, all connections are clean as well as all grounds, all new hoses and vacuum tubes so there are no vacuum leaks, tank is resealed, new filter, yada yada.

I have performed all the tests on page 32-33 of the FI bible "Engine Will Not Start" most were all good with these few exceptions  Bruce, I did your modified test for injector clicks, I never once got a spark from the center coil wire to ground and when grounding and ungrounding the Neg side of the coil, sometimes the injectors clicked every 3rd time, some every 2nd time and some two times in a row and that was the same for all six. No pattern that I could see.

Fuel pump works when it is suppose to but I never heard the fuel regulator buzzing, also I only have a 21 psi fuel gauge hooked up but it takes 4-5 sec for the fuel pressure to ramp up to 21psi and as soon as I stop cranking the pressure needle backs down at the same speed so there is virtually no pressure in the line by the time I get over to fuel line and open it.(I suspect this is the real problem)

While cranking the engine there is some back firing and puffing out of the AFM.  The damned thing is I had the engine running roughly for about a minute on Sunday then I turned it off the get the camera ready to shoot a little video but couldn't get it going again.

Open to suggestions from anyone.

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you have to figure out the fuel pressure. Make sure you have gas in tank (BTDT), check voltage ATTHE PUMP, should be around 10-11volts this pump on engine off, however you get that to be.

could be the FPR is just flowing too much back, you will need to do a dead head test (leave gauge on and BRIEFLY clamp off the return hose), only long enough to see the max pressure the pump can provide, like 1 second. Do this 1st before the voltage test, its easy and fast. I think the OE style pump will max out at about 60psi, it has a bypass that prevents too much pressure. After market pumps can go up to 100 psi fast and will locate any weak hoses or connections in dramatic fashion (gas spraying everywhere as hose burst). This is why you only want to do it for a second and get a quick read, before things to bad.

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2 hours ago, grannyknot said:

I never once got a spark from the center coil wire to ground and when grounding and ungrounding the Neg side of the coil, sometimes the injectors clicked every 3rd time, some every 2nd time and some two times in a row and that was the same for all six. No pattern that I could see.

Well the lack of a pattern doesn't concern me that much. It's supposed to click the injectors every third ignition event, but doing it with a wire as I suggested is likely to result in a lot of contact "bounce" and what you are thinking is one connection may actually create two, three, or even more contacts. So I'm not too concerned about that. Yet.

The complete lack of spark, however, is something that needs investigation.

So what happens if you connect everything up normally and pull one of the spark plug wires off and stuff a spare plug into the wire and lay it on the valve cover while you crank the engine? Do you get a nice snappy blue spark? Is the ignition system stock 77 style? Or are you running some aftermarket system?

2 hours ago, grannyknot said:

Fuel pump works when it is suppose to but I never heard the fuel regulator buzzing, also I only have a 21 psi fuel gauge hooked up but it takes 4-5 sec for the fuel pressure to ramp up to 21psi and as soon as I stop cranking the pressure needle backs down at the same speed

And I'm not exactly sure what you mean by this... Are you saying that the fuel pressure gauge you are using tops out at 21 psi? And you are pegging it at that value? If that's the case, then you might not have a pressure problem. You just don't know what the pressure is... Only thing you know is it's higher than 21?

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Yes, with a spark plug wire pulled and grounded during cranking I get a good fat spark. The ignition system is stock.

The fuel pressure gauge I have only goes to 21 psi, it is mounted between the fuel filter and the fuel rail, the needle doesn't really "peg" it creeps up. I checked it again last night after posting and it is taking even longer to get up to the peg and then the pressure releases.

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15 hours ago, grannyknot said:

Fuel pump works when it is suppose to but I never heard the fuel regulator buzzing, also I only have a 21 psi fuel gauge hooked up but it takes 4-5 sec for the fuel pressure to ramp up to 21psi and as soon as I stop cranking the pressure needle backs down at the same speed so there is virtually no pressure in the line by the time I get over to fuel line and open it.(I suspect this is the real problem)

While cranking the engine there is some back firing and puffing out of the AFM.  The damned thing is I had the engine running roughly for about a minute on Sunday then I turned it off the get the camera ready to shoot a little video but couldn't get it going again.

Your instincts seem on target.  Fuel pressure should climb rapidly to the FPR limit.  Back (front) firing out of the intake manifold is the "lean mixture" sign.

Fuel pressure leak-down means that either your FPR or your pump check valve are bad, or leaky injectors.  A good system should hold pressure, at least 20-30 psi for weeks or months.

Are you using starting fluid just to be sure that timing is right, in between your fuel system troubleshooting?

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8 hours ago, Zed Head said:

Are you using starting fluid just to be sure that timing is right, in between your fuel system troubleshooting?

No I haven't used ether yet but I set the distributor back to exactly where it was when the engine was idling well before tear down.  I picked up the Walbro replacement fuel pump today so I should have that installed by tomorrow afternoon, hopefully that will do the trick.

I also have a spare FPR so I'll get that ready just in case.

 

IMG_0841.JPG

IMG_0842.JPG

Edited by grannyknot

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The new Walbro fuel pump is installed, still don't know the exact fuel pressure but the needle pegs at 21psi and stays there after I stop cranking but still no start. Still backfiring and puffing out the AFM.

Not sure of the next step, get a proper fuel pressure gauge, change out the FPR for my spare or a new one, go back and do the No Start tests again, or maybe find a new /77 ECU ? This really isn't my strongest area.

Thanks

 

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Installed a proper fuel pressure gauge today, turned the key to start and the needle goes up to about 35 psi and stays there, I clamped off the hose after the gauge and let the pressure get up to 60 psi then unclamped the hose and it came back down to 35 psi so looks like the FPR is working, do you guys agree?

I have gone through all the tests from page 47 to 71 and all were good except for test #1-3b air flow meter, resistance, ohmmeter leads between pin 7 and pin 8, there is suppose to be a small amount of resistance but continuity. My resistance was 144 ohms which doesn't seem small.  Also, test #3 - 3 cold start system circuit, voltmeter leads positive to pin 21, negative to ground, the results should be; Little to no voltage at first; then battery voltage after no more than 15 sec. My result was battery voltage almost immediately.

So still no start, I guess I'll pull the cold start valve tomorrow and maybe exchange it for my spare. Any patterns emerging to you sparkys out there?

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1 hour ago, Dave WM said:

do you hear the injectors clicking when cranking the engine?

I think they are, the starter is too noisy to separate out the injector clicking. I did pull the spark plugs today and they were wet with gas.  Maybe I should pull the whole injector pack and fuel rail unit and see if they are spraying and or dripping. Grasping at straws now.

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Fuel pressure sounds fine.

Don't worry about the  test #3 - 3 cold start system circuit when it showed voltage immediately. All that means is that your cold start injector never fired. Either your thermotime switch is burned open, or it was just too warm to close, but in any event, that's not what's causing your problem. I've been running with no cold start injector for years now, and it takes a little longer to start, but it still starts.

And I will double check my notes, but I don't think your AFM test #1-3b is a problem either.

Can we go back to basics....

Are you 1000% sure you have the firing order correct?
Are you 1000% sure you have the ignition timing correct?
Are you 1000% sure you are getting good spark on more than just one plug?

 

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wet plugs means getting gas, good.

agree with CO, sounds more like an ignition problem. put crank at #1 TDC make sure cams are bunny ears (both up, valves closed, firing position). Confirm rotor is pointing to #1 on the cap.

I assume you have a timing light, use it to make sure timing is about 10 degrees advanced.

Edited by Dave WM

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To use @siteunseen's phase,  I bow down in shame.  The engine is running fine now, my mistake is so humiliating I can't even admit to it yet. Thanks for your help guys I certainly know the FI system inside out now.

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out with it, no shaming will be done, we all done stupid things, ask me about using vice grips to hold the TB open then slamming the hood down forgetting to remove them...

 

shall we guess, dist on backwards?

Edited by Dave WM

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Timing ! 

We all make the mistakes . My latest project my Nissan 720 I put the dizzy 180 degrees out on my brand new rebuild .  Just wasn’t paying close enough attention . But wait - still wouldn’t start, just sputtered . Find out later that my carb adapter was not tight - AT ALL! Sucking a little too much air . After that engine fires right up 

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