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post #1 of 12 (permalink) Old 07-16-2019, 04:26 PM Thread Starter
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mystery starting/fuel issues

So I recently pulled the engine out of a '87 Platinum that had been largely neglected by a previous owner but was running well. I cleaned it and swapped many parts (mounts, belts, plugs, water pump, lines and hoses, etc...). Upon reassembly it started very briefly, and has only occasionally started for a few seconds since. I am at my wit's end trying to figure out what I got slightly wrong on reassembly!

I feel it must be something very minor and silly as the car can start occasionally and sounds healthy until it sputters to death. This indicates to me all the major stuff is right, and leads me to believe that there is most likely a fuel issue.

Most times I have tested it, moving the AFM flap causes the fuel pump to activate, but friday and this morning it didn't. I wanted to confirm the fuel pump was still good, so this morning I jumped 12V to the fuel pump directly and it ran fine. After this, the car started and ran for ~5 seconds, its longest run since the engine out work. It seemed that the car was functioning perfectly except for the fuel pump and died when the fuel in the rail was exhausted.

After some more electrical checks and parts swapping I have the pump working as expected again, but the car won't start. The cold start injector seems stuck open though, as when I ran the fuel pump fuel poured out the intake hose.

My guess had been that I have a situation where I either get the injectors to fire or the fuel pump to run but not both. Since I don't know how this is possible and the CS injector runs whenever the fuel rail is pressurized, I now think I may have a bad ground situation that keeps all injectors open at all times, but I'm not sure how to further diagnose as the grounds I know of seem secure and I have misplaced my multimeter (I'm borrowing one for my next stab at this!). Any pointers would be much appreciated to get me back on the road!

I can provide pictures or photos if needed, let me know what you need to see!

Thanks!
Steven
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post #2 of 12 (permalink) Old 07-16-2019, 06:14 PM
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Bad grounds can cause a few problems but they will not cause the injectors to stay on. If you suspect that the cold start injector is sticking on then clamp the hose after the car has briefly started. If you suspect fuel pressure then buy a fuel pressure gauge and T it into the CSI hose. If you suspect that the injectors are not firing then pull the distributor, turn on the ignition and spin the distributor by hand and listen for the clicking of the injectors and the cracking of the spark plugs.

Ed Prytherch
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A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #3 of 12 (permalink) Old 07-16-2019, 09:10 PM
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Did you remember to connect the injector grounds to the back passenger side of the cam cover? It sounds like you are running on the CSI fuel.

Kevin

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post #4 of 12 (permalink) Old 07-17-2019, 04:56 AM
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Quote:
Originally Posted by kredden View Post
Did you remember to connect the injector grounds to the back passenger side of the cam cover? It sounds like you are running on the CSI fuel.

Kevin
+1, I did this recently on my GTV6, start for a few seconds each time, tried throttle and got plenum pop. Found I left the grounds off, installed and it sprang to life, no issues after that.

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post #5 of 12 (permalink) Old 07-17-2019, 06:06 AM Thread Starter
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The injector grounds are attached, but there is a chance they have bad contact. I’ll clean the contacts for those grounds and then try the distributor and fuel checks alfaparticle suggested and report back on the results
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post #6 of 12 (permalink) Old 07-19-2019, 02:27 PM Thread Starter
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Originally Posted by alfaparticle View Post
Bad grounds can cause a few problems but they will not cause the injectors to stay on. If you suspect that the cold start injector is sticking on then clamp the hose after the car has briefly started. If you suspect fuel pressure then buy a fuel pressure gauge and T it into the CSI hose. If you suspect that the injectors are not firing then pull the distributor, turn on the ignition and spin the distributor by hand and listen for the clicking of the injectors and the cracking of the spark plugs.
Tried the spin the distributor thing and caused a huge plenum pop. It happened so fast I’m not sure if the injectors fired or gas vapor was just there. Didn’t expect this result at all, but probably shouldn’t have done it with the afm removed and unlimited air available, huh?

Tried it again with the coil disconnected so I couldn’t spark it again, got some clicks for sure in the coil, but honestly
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post #7 of 12 (permalink) Old 07-19-2019, 02:32 PM Thread Starter
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Pop, hit send half done!

Honestly can’t tell if the injectors made any sound. There was a pattern of a couple softer clicks then one heavier click. I took a video of what it sounded like but not sure how to attach on mobile, this link might work to go to it?

https://share.icloud.com/photos/0pmT...VgA#Amelia,_OH

It’s still my best guess that the injectors aren’t firing, going to clean the grounds now and see if that helps
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post #8 of 12 (permalink) Old 07-19-2019, 02:38 PM Thread Starter
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Also, just realized I had not connected the electrical connection to the aux air valve. Going to put it all back together with that connected, might be the magic bullet somehow!
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post #9 of 12 (permalink) Old 07-21-2019, 10:15 AM
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Any luck?

Kevin

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post #10 of 12 (permalink) Old 07-21-2019, 12:18 PM
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The wires to the AAV valve are to slowly close it after a cold start. I doubt that it has any impact on your problem.

The grounds are not from the injectors. There is a set of them from the L-Jet computer for the injector circuits, there is a separate computer ground for sensor circuits and there are sensor grounds. They all need to be good. The coolant temperature sender ground is at the thermostat housing and I think that all of the others are grouped together and attached by a cam cover screw.

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post #11 of 12 (permalink) Old 07-22-2019, 09:00 AM Thread Starter
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https://share.icloud.com/photos/0NYy...ktA#Amelia,_OH
Not sure if those links got to anything, but hope someone can see the video.

Finally got it back together and it started very rough/strange. Started after I stopped cranking it and had a super rough, slow, and stumbling idle. Then evened out slightly with minimal gas and popped the plenum again at about 500 indicated rpm.

Definitely thinking it’s in the timing/tuning now as everything seems to be working after reassembly and cleaning all the ground contacts.

Anyone have any further advice or thoughts?

My next steps are checking the ignition timing, searching for any big air leaks/poorly installed new vacuum lines, and hoping it’s not something more than that
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post #12 of 12 (permalink) Old 07-22-2019, 10:30 AM Thread Starter
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After messing with the distributor nothing got smoother so I smoke tested the intake and found that one of the plenum to intake runner hoses had split open, likely during one of the plenum pops.

I’m going to swap those hoses out with new ones and should be home free when I’m leak free!

Not sure what actually fixed the no start issue (probably cleaning the grounds again honestly) but it sure seems resolved for now!

Thanks for the advice everyone and I’ll update when I get the new hoses on the plenum and everything is well again!
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