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No Start

Tiny
PATRICK FLOHE
  • MEMBER
  • 1988 BUICK CENTURY
  • 2.5L
  • 4 CYL
  • 190,000 MILES
Latest is that I did a compression test today, after verifying fuel is being sprayed, and will not start with starting fluid.

Here are the results:
Compression Test
#1: 126
#2: 92 / 97
#3: 120 / 124
#4: 107 / 112

-Not very comforting numbers
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Tuesday, March 21st, 2017 AT 4:09 PM

9 Replies

Tiny
STEVE W.
  • MECHANIC
  • 12,975 POSTS
Even with that compression I would think it would start, it will not run the best but it should at least run. (GM calls for 100 psi minimum)

Have you tried to start it at partial throttle? How about the IAC valve If it was open too far it could be too lean to start. Same with a sticky EGR.

You could check the timing just to see if the ECM is working. You need a magnetic probe style unit.

Not much else I can think of at the moment.
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Tuesday, March 21st, 2017 AT 10:44 PM
Tiny
PATRICK FLOHE
  • MEMBER
  • 20 POSTS
I did try to start at partail throttle, earlier today.

I thought about the IAC, but it definitely was getting good fuel.
I could see very good fuel spray, plus, like I said in my earlier posts, it has excellent spark.
I did verify that the EGR is free and smooth.

I thought it should run too.A friend of mine said a V6, yes, and would run crappy. Not the 2.5.
However, I once had a '87 2.5 with a hole in the center of #3 piston, big enough to stick your finger through. It ran rough, but it ran.
They are good engines. I put a new piston and gaskets in it, and it ran like a champ.
-After some valve adjustment washers!
I love them. No timing chain, just timing gears.
This has been well-cared-for. I cannot believe this happened, but it is at 190,000 miles.
I have heard of a few people getting over 300,000 miles on these.

I guess I change the head gasket & associated gasket set.
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Tuesday, March 21st, 2017 AT 11:10 PM
Tiny
STEVE W.
  • MECHANIC
  • 12,975 POSTS
They are one of GMs better engines. I have seen them run with much lower compression and a plug out. About the only item left would be if the ECM isn't doing timing control.
How about a more direct approach. Pull the plugs, put some gas into each cylinder and see if it fires then?
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Wednesday, March 22nd, 2017 AT 12:19 AM
Tiny
PATRICK FLOHE
  • MEMBER
  • 20 POSTS
I could do that, but the MAT sensor was wet with fuel, and the plugs were wet with fuel too.
I saw it spraying plenty of fuel during Start attempts, and I know the plugs were firing. At least prior to this start attempt. I tried all the plug wires first and then after gapping, put the plugs into the wire boot, and verified they sparked. They gave a strong spark.
Would they not fire, being wet with fuel?

I just cannot believe it would have such strong spark, and fuel, and still not start.
It does not backfire, so I do not think it is sparking at the wrong time, and it cranks like it is not out of time. Usually, in my experience, if the timing is off, it sounds different when cranking.

What do you think?
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Wednesday, March 22nd, 2017 AT 8:42 AM
Tiny
STEVE W.
  • MECHANIC
  • 12,975 POSTS
Wet plugs will not fire. Pull them all crank the engine with the throttle held wide open, that should put it in clear flood mode and stop the injectors from adding fuel. That should dry the cylinders. Clean the plugs and see what you get. It is possible that the injectors are adding excess fuel and that is simply keeping it from firing. That would be ECM related.
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Wednesday, March 22nd, 2017 AT 9:02 AM
Tiny
PATRICK FLOHE
  • MEMBER
  • 20 POSTS
It only has one injector, but that thought did occur to me.
The wetting could've come from my part-throttle start attempt.
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Wednesday, March 22nd, 2017 AT 9:16 AM
Tiny
STEVE W.
  • MECHANIC
  • 12,975 POSTS
Check the fuel pressure, if it is running high from a bad regulator it could be dumping fuel. Easy thing to try, Clear the engine. Disconnect the injector wiring then shoot just a quick spray of starting fluid while cranking the engine. See if it fires that way. Then reconnect the injector and try again. If the plugs get wet again then you have a rich condition.
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Wednesday, March 22nd, 2017 AT 9:26 AM
Tiny
PATRICK FLOHE
  • MEMBER
  • 20 POSTS
Will-do, when I get back there.
Do you know what the fitting size is on that? I'll need an adaptor. The last kit I rented for that, didn't have a proper adaptor in it.
I have to disconnect / tap into the hard line, as the old 2.5s don't have a valve stem port, like my other cars do.

The presssure regulator is actually on the Throttle Body, so there's no way for me to check the pressure downstream of that.
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Wednesday, March 22nd, 2017 AT 4:30 PM
Tiny
STEVE W.
  • MECHANIC
  • 12,975 POSTS
The pressure you see in the system is the pressure that the regulator is feeding the system on the TBI units. 9-13 psi is normal.

I don't remember the size off hand, been a while since I used the adapter. Yeah the schrader port makes it a lot easier, till they leak!
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Wednesday, March 22nd, 2017 AT 6:08 PM

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