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Why is compression so low?
I've posted about this car before, engine rebuilt and still won't
start... Old post - http://groups.google.com/group/alt.a...95d910a2?hl=en The thing is... I said all cylinders have compression, but I never asked my buddy what the compression was. So, today I checked for myself, and saw that the cylinders only had 90ish compression, and I'm reasonably sure that's the reason the car won't start. The rings and valves were all replaced, everything was torqued back to factory specs with new gaskets blah blah... any ideas on why the compression is so low? |
Re: Why is compression so low?
In article <1168235571.989073.42830@s80g2000cwa.googlegroups. com>, fascion wrote:
> The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? Didn't read the old post, but if everything is new and good, then the timing of the valves may not be 'in phase' with the crank. As if the timing chain or belt skipped a tooth or three. |
Re: Why is compression so low?
In article <1168235571.989073.42830@s80g2000cwa.googlegroups. com>, fascion wrote:
> The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? Didn't read the old post, but if everything is new and good, then the timing of the valves may not be 'in phase' with the crank. As if the timing chain or belt skipped a tooth or three. |
Re: Why is compression so low?
In article <1168235571.989073.42830@s80g2000cwa.googlegroups. com>, fascion wrote:
> The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? Didn't read the old post, but if everything is new and good, then the timing of the valves may not be 'in phase' with the crank. As if the timing chain or belt skipped a tooth or three. |
Re: Why is compression so low?
"fascion" <onefortyseven@gmail.com> wrote in message
news:1168235571.989073.42830@s80g2000cwa.googlegro ups.com... > I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? > I'm with Brent - recheck the valve timing (the timing marks on the cam pulleys compared with TDC). I bet you will find it at least one tooth off. 90ish compression won't prevent an engine from starting but valve mistiming - which usually shows up as gross ignition mistiming - sure will. Be sure to pull the engine through by the crank turning only CCW or the belt will jump more. In the original thread I saw you set the ignition timing by eyeball on the distributor, but you will need a timing light to get it close enough to run right... maybe even to run at all. First check the valve timing by the marks. When the valve timing is right the distributor should go right back where it was originally and it should be good. Mike |
Re: Why is compression so low?
"fascion" <onefortyseven@gmail.com> wrote in message
news:1168235571.989073.42830@s80g2000cwa.googlegro ups.com... > I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? > I'm with Brent - recheck the valve timing (the timing marks on the cam pulleys compared with TDC). I bet you will find it at least one tooth off. 90ish compression won't prevent an engine from starting but valve mistiming - which usually shows up as gross ignition mistiming - sure will. Be sure to pull the engine through by the crank turning only CCW or the belt will jump more. In the original thread I saw you set the ignition timing by eyeball on the distributor, but you will need a timing light to get it close enough to run right... maybe even to run at all. First check the valve timing by the marks. When the valve timing is right the distributor should go right back where it was originally and it should be good. Mike |
Re: Why is compression so low?
"fascion" <onefortyseven@gmail.com> wrote in message
news:1168235571.989073.42830@s80g2000cwa.googlegro ups.com... > I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? > I'm with Brent - recheck the valve timing (the timing marks on the cam pulleys compared with TDC). I bet you will find it at least one tooth off. 90ish compression won't prevent an engine from starting but valve mistiming - which usually shows up as gross ignition mistiming - sure will. Be sure to pull the engine through by the crank turning only CCW or the belt will jump more. In the original thread I saw you set the ignition timing by eyeball on the distributor, but you will need a timing light to get it close enough to run right... maybe even to run at all. First check the valve timing by the marks. When the valve timing is right the distributor should go right back where it was originally and it should be good. Mike |
Re: Why is compression so low?
fascion wrote:
> I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? > Cam timing way off? If the valves open and close at the wrong times, it won't build proper compression. |
Re: Why is compression so low?
fascion wrote:
> I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? > Cam timing way off? If the valves open and close at the wrong times, it won't build proper compression. |
Re: Why is compression so low?
fascion wrote:
> I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? > Cam timing way off? If the valves open and close at the wrong times, it won't build proper compression. |
Re: Why is compression so low?
That can happen when the timing belt or chain is installed. If the
timing isn't right the valves don't close at the right times to get full compression. If the rings are no good or won't seat, that can blow the compression out too. You can try a spoonful of oil into the plug hole just before testing the compression again. If the compression comes up, you have faulty rings, if not, look to the valve timing. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) fascion wrote: > > I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? |
Re: Why is compression so low?
That can happen when the timing belt or chain is installed. If the
timing isn't right the valves don't close at the right times to get full compression. If the rings are no good or won't seat, that can blow the compression out too. You can try a spoonful of oil into the plug hole just before testing the compression again. If the compression comes up, you have faulty rings, if not, look to the valve timing. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) fascion wrote: > > I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? |
Re: Why is compression so low?
That can happen when the timing belt or chain is installed. If the
timing isn't right the valves don't close at the right times to get full compression. If the rings are no good or won't seat, that can blow the compression out too. You can try a spoonful of oil into the plug hole just before testing the compression again. If the compression comes up, you have faulty rings, if not, look to the valve timing. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) fascion wrote: > > I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? |
Re: Why is compression so low?
fascion wrote:
> I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? > =================================== If you failed to prop the throttle open, and the engine was dry, the compression will be WAY LOW. You may have damaged the igniter too when you cranked with the wires disconnected. Have you listened to the fuel pump, and tried a bit of starting fluid to see if it will fire up even for a second? 'Curly' |
Re: Why is compression so low?
fascion wrote:
> I've posted about this car before, engine rebuilt and still won't > start... > > Old post - > http://groups.google.com/group/alt.a...95d910a2?hl=en > > The thing is... I said all cylinders have compression, but I never > asked my buddy what the compression was. So, today I checked for > myself, and saw that the cylinders only had 90ish compression, and I'm > reasonably sure that's the reason the car won't start. The rings and > valves were all replaced, everything was torqued back to factory specs > with new gaskets blah blah... any ideas on why the compression is so > low? > =================================== If you failed to prop the throttle open, and the engine was dry, the compression will be WAY LOW. You may have damaged the igniter too when you cranked with the wires disconnected. Have you listened to the fuel pump, and tried a bit of starting fluid to see if it will fire up even for a second? 'Curly' |
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