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Re: Exhaust manifold temperatures
Posted: Wed Mar 21, 2018 12:56 pm
by DaveEFI
Rule 1. Eliminate the easy things before thinking the worst.
Re: Exhaust manifold temperatures
Posted: Wed Mar 21, 2018 3:32 pm
by Quagmire
Shame its #7 and therefore a bit tricky to get to easily - you can quite often feel the injectors bodies clicking as they operate if you put a finger on them with the engine running.
No clicky = no worky.
Re: Exhaust manifold temperatures
Posted: Wed Mar 21, 2018 3:51 pm
by DaveEFI
Use a stethoscope?
Re: Exhaust manifold temperatures
Posted: Thu Mar 22, 2018 2:00 pm
by Quagmire
Could work!
Or you could touch the tip of a very long screwdriver on the injector body and listen to the handle.
Re: Exhaust manifold temperatures
Posted: Mon Mar 26, 2018 8:12 pm
by paulsv8manta
Well guys I believe I've found the problem, caused by, yes you've guessed it me!
I decided to strip down the fuel rail and in my lack of wisdom I had painted the fuel rail and found the petrol was slowly melting the paint off and clogging the injectors. No.7 was the worse but there was crud in all of the injectors, I've back flushed them all with petrol and a final flush through with redex. They are now all working fine, I won't be able to test it out till next week when the rocker cover gasket arrive.
I will let you all know the outcome then.
I did find this little snippet.
Measure Exhaust Manifold Temperatures
If a fuel injector will not close, it will dump gasoline on the catalyst that opens and closes the valve, causing it to overheat and burn out. This will produce high temperatures at the exhaust manifold while the engine is warm. If the valve will not open, an excessive amount of oxygen will disable the catalyst, producing excessively low temperatures at the exhaust manifold. To determine whether this is an issue, point a laser thermometer at the pipes of the exhaust manifold while the engine is warm. A normal reading on each cylinder will be within 30 degrees of 450 degrees Fahrenheit. An injector that will not open will yield a temperature of 200 to 250 degrees and an injector that will not close will show temperatures of 600 degrees or more.
Re: Exhaust manifold temperatures
Posted: Mon Mar 26, 2018 9:00 pm
by sidecar
paulsv8manta wrote: ↑Mon Mar 26, 2018 8:12 pm
Well guys I believe I've found the problem, caused by, yes you've guessed it me!
I decided to strip down the fuel rail and in my lack of wisdom I had painted the fuel rail and found the petrol was slowly melting the paint off and clogging the injectors. No.7 was the worse but there was crud in all of the injectors, I've back flushed them all with petrol and a final flush through with redex. They are now all working fine, I won't be able to test it out till next week when the rocker cover gasket arrive.
I will let you all know the outcome then.
I did find this little snippet.
Measure Exhaust Manifold Temperatures
If a fuel injector will not close, it will dump gasoline on the catalyst that opens and closes the valve, causing it to overheat and burn out. This will produce high temperatures at the exhaust manifold while the engine is warm. If the valve will not open, an excessive amount of oxygen will disable the catalyst, producing excessively low temperatures at the exhaust manifold. To determine whether this is an issue, point a laser thermometer at the pipes of the exhaust manifold while the engine is warm. A normal reading on each cylinder will be within 30 degrees of 450 degrees Fahrenheit. An injector that will not open will yield a temperature of 200 to 250 degrees and an injector that will not close will show temperatures of 600 degrees or more.
Is the paint in the inside of the fuel rail?
Re: Exhaust manifold temperatures
Posted: Tue Mar 27, 2018 7:34 pm
by paulsv8manta
Hi sidecar, I had painted right up to the barbed end, then the short hose of the injectors slides right over the whole part.
Re: Exhaust manifold temperatures
Posted: Fri Mar 30, 2018 8:57 pm
by Seight-V8
be careful about how your IR thermometer reads the temperature from shiny surfaces, if your manifolds are polished or dull, even heat glazing can make a difference to the readings shown on the IR display, emissivity of the surface is important, on some guns you can change this depending on the surface you are measuring it from.
You will get better more accurate readings from using a thermometer fixed probe placed against the same place on the each header.
Unfortuneatly its part of my day job to know these things.....
Just be careful your not finding a problem that is not there.
google it if you need to know more.
regards
scott
Re: Exhaust manifold temperatures
Posted: Tue Apr 10, 2018 10:29 am
by paulsv8manta
Well it’s all put back together and started up. It looks like no.7 had never really run as smoke came off of the exhaust pipe (I had painted the exhaust manifolds with high temperature paint.)
Did a temperature test and found no.2 not running!
Stripped it all down yet again and found a foreign body. Hopefully I’ll have it all put back together tonight.
Re: Exhaust manifold temperatures
Posted: Wed Apr 11, 2018 1:22 pm
by SuperV8
The good thing with separate headers is its easy to narrow down a misfire to a particular cylinder.
Mine have exhaust wrap so you can touch them for a second. When I was chasing a misfire I could easily tell by touch.
Tom.