77 280 cold start vs main injectors

Zed Head · December 7, 2015

Compression is 110, 90, 125, 110, 110, 110. Found TDC and checked/reset the destributor multiple times, to be sure.

I was just pointing out some things to check. By "ignition timing mark is twice right", I meant that the timing mark will be on the pointer on TDC for the exhaust stroke also, in addition to compression stroke. If you don't check the cam lobes and/or the timing chain sprocket mark, you can get fooled. As Greg W. illustrated.

It comes to mind mainly because you said that you have spark, but you don't even get a pop with starting fluid. Spark on the exhaust stroke is spark in to a wide open cylinder. Nothing will happen.

Do you have a strong blue spark, or a weak orange one? I've had weak spark outside the engine that won't start it when the plugs are installed. But even then starting fluid would get it going. Something not right if starting fluid doesn't get a reaction.

rosaluma · December 7, 2015

On another note, gwri8....help a brother out with the brackets to install 240 bumpers on a 280. I have the bumpers, but have struck out with brackets.

Gratefully,

Zed Head · December 7, 2015

Still doesn't explain why the injectors are not receiving any signal from the ECU but, as you can tell, I am chasing anything.

In the past, when I had the stock ignition system, I found that the ECU would not fire the injectors if the tachometer was disconnected. Never understood why, and it doesn't happen with the GM HEI module, but it happened on two separate cars with the stock ignition module. Something to confirm.

gwri8 · December 7, 2015

I used stock 240 brackets for the front bumper. I had to re-bend them to shape, but it's not too difficult if you have a vise. You can eyeball it and adjust from there. They bolted right to the frame in existing holes on my 77'. You could make your own it you wish with some steel bars with the right gauge and big drill bit. I have not done the rear bumper yet, still not sure I want one. Do a search, there is quite a bit of info about how to attach 240 bumpers to 280's.

rosaluma · December 7, 2015

Zed, found your comment on another thread about AFM ground. I am not confident I have it properly grounded. Will update tomorrow.

siteunseen · December 7, 2015

What about the EFI power connector at the battery?

rosaluma · December 7, 2015

Attached are pictures of the engine. I do not have the EFI ground in the picture provided by siteunseen. Will try to attach the video of attempt to turn it over. Note the second half of the video when the engine struggles less is when the clutch pedal is actually NOT engaged, which concerns me as to whether the fork on the throwout bearing is installed properly, after we replaced seals and bearing.

car.wmv

Edited December 7, 2015 by rosaluma

Zed Head · December 7, 2015

When you press on the clutch pedal you're actually putting force on the crankshaft thrust bearings. Might be why there's a little relief when you let the pedal up.

Since you have cylinder pressure, and spark, the most rational reason for no-start, to me anyway, is a timing issue. Fuel, compression, and spark have to occur at the proper times to get combustion. Starting fluid is fuel (along with oxygen), you have compression, and you have spark. That leaves timing, Timing of everything, not just ignition.

And you do have the EFI ground, I can see it in your picture by the battery. And the AFM ground is one of the things that you test for in the Injection Guidebooks. But you're mixing your acronyms, which is a concern.

Many many people have been in your situation. The best thing you could do is to make a list of all of the things you've tested, with real numbers (not "continuity"), and to confirm the things that people ask you to confirm. Like making sure that the distributor rotor is pointing at the #1 cylinder (the one in front), at the same time as the notch is aligned with the groove on the sprocket and cam shaft retaining plate. Those things are the very most basic of things that need to be confirmed. People often assume that they're right, when they're not.

A video of an engine cranking but not starting doesn't give us the numbers we need. And give details on how you did things, like testing for spark. You can get spark at the main wire from the coil, then forget to put the rotor on the distributor. You'll "have spark" it just won't be getting to where it needs to be.

Time to get meticulous.

rosaluma · December 7, 2015

Thanks for your patience and help. I checked spark by pulling the plugs, had them laid out on the fender when i turned the engine over, all plugs sparked blue...checked gap, etc. Will pull the valve cover off and check the location of the notch on the cam sproket, again, when 1 is at compression.

I do not have the EFI ground that is near the CSV conn in siteunseen's picture.

Zed Head · December 7, 2015

I see now. That is actually just a harness ground, the picture is not-quite-right (I think that picture came from the interweb). It's just an eyelet end on a wire coming out of the bundle of wires there.The EFI ground is the red cable over by the battery. Still, best to check grounds at the ECU connector or whichever device needs them. Then you know that they actually work.

Here's a thought - you might have a huge vacuum leak. Maybe forgot to connect the PCV hose under the intake manifold, or you have a split hose somewhere. That could lean everything out so much that the fuel just blows through without lighting.

siteunseen · December 7, 2015

If his 77s like mine was, put a mirror under the egr valve and look for a rotted out hole in the intake.

FWIW

rosaluma · December 7, 2015

I remove #1 spark plug, and install small dummy plug. When the dummy plug pops, I have #1 at compression. Crank is at TDC, rotor on distributor is at #1. Plug wires are all in proper sequence, 153624, counter clockwise. Oil pump shaft (new) is about 5-7 degrees off of two holes in distributor mount. Turn key to start, no start. Cold start valve injector is firing...see light. Main injectors do not light. Fuel pressure is at 36 psi. Fuel pump engages when switch activated in the AFM intake flap is pushed. Timing gear at the cam is set near the notch on the face plate of the cam. Car still does not start, even with starter fluid.