a guy i know whos a good mechanic told me an easy way to test compresstion was to take out the plugs have someone crank it while I hold min tumb over the hole. I did each plug and all seemed very strong except one. On the weak plug I could barely feel anything but a small push.

 

its the number 6 cylinder

 

Could be a bent valve from an earlier start with no lube on the valve guides, the valves can sometimes be a bit lazy coming back on the spring. This happened to me !! Easy check is to check out the tappet gap.

 

ok, if that is the case and 5 of the 6 are working ok comp wise and all else was ok wouldnt it at least start and run crappy? i think there's still an issue with something stopping the injectors from working. there is no click still even with new injec and loom...........and thanks for replying FM

 

Hello Tudstuen,
Have you checked the power relay for Ign.
It fires the computor,
There are three relays on ther firewall
1 red Start if it is cranking it works.
2 Thermotime controls cold start injector
# power relay for computor, without a feed to the lerge brown and I think white or slate wire, No computor! you can check the feed, turn on Ign remove cover from rear bulkead in trunk and with a test light check for feed on the large brown and again maybe slate wire, this fires up the computor for fuel,
has nothing to do with spark.
Just changed a limo over to fuel infection and had a little go round with this myself, plenty spark no start without brake cleaner
Dont start tearing the valve covers off yet, Also a large group of ground wires at rear of intake on the last water rail bolt, put a jumper to a Known ground
ie, Battery with a GOOD ground here No start.
Good luck,
Donald.

 

On my last,
Read without a GOOD ground here NO spark.
My Bad.
Donald.

 

everything you post ive done. and i get good pressure at rail. Ive taken of the ground wires at rear water rail and cleaned good. i have not tryed the jumper there. i will today thanks.. i really dont want to rip the engine down.. something keeps saying its something stupid....................also what kind of ground wire works best just a regular with leads of should it have a gator clip for the bat terminal

 

i did the jumper to the neg bat term and did the paper clip trick on the CTS. no change.

 

If the O2 sensor is bad could it make a no start like what we've discussed

 

No.

In fact the O2 sensor doesn't even come "on line" for a couples minutes after engine start and even then it trims the mixture....doesn't outright turn fueling on/off

On the very odd chance that the sensor is shorting out or back-feeding or some such bizare thing you could disconnect it and see if anything changes

Cheers
DD

 

One low cylnder should not prevent the engine from starting

Cheers
DD

 

This has to be something related to the injectors, because they are the only thing I have found not to work. Great spark, fuel pressure and delivery to the rail, but the injectors are not working.




I noticed last night that if you crank the engine, the tach will jump up to around 1500 RPM or so for a sec and back to zero. It hops as you crank it.


I am stumped.

 

everyone is stumped.

check the following from the Service Manual and see if your Main Relay is good, I suspect it isn't.

 

ive changed around the relays one being new. and attempted start. after Jose's post i took the new one from the pump relay and put it in the main and attempted start. when I did this the pump ran and could hear it pressurize. again this was without the key turned. so i tried to start and no go. but.....the fuel being pumped before the key was turned is odd .........any idea's

 

Are the "main" and "fuel pump" relays the originals? With the silver metal casings?

Either way, remove them and check the terminal designations on the bottom.

You should have 30-85-86-87-87

If you have 30-85-86-87-87A, you have incorrect relay(s)

Grapsing at straws but that's all we have left

Cheers
DD

 

they are brown plastic and have 87 not 87 A..thanks

 

maybe you have the wrong relays in the wrong locations? (unless the two relays are identical). otherwise I've never seen them in Brown, always a metal case. The Diode Pack "relay" is Red.

 

there is another relay, the Start Lock Relay behind the dash. Have you checked that the black wiring plug is correctly seated below that relay? it's very easy to mis-connect those relays behind the dash and miss one of the connecting "legs".

 

the last check I can think of is the AFM. And that can only be done by substitution.

 

i dont know what that is..behind the dash where?