Injector Q? and compression test questions

nejones · Nov 2nd, 2007, 19:19

Just a couple of questions really.

1990 760t b230ft - what type of fuel injector (make, model etc) is fitted on this car?

Did a compression test today on the above engine. First time i've done a compression test so bear with me here please!

Removed all the plugs and isolated the coil. I wound the tester into #1 without using the 'solid' adaptor on the bottom of the tube (the adaptor has a longer thread than that on the end of the rubber tube). I got a reading of 150psi. Then I used the adaptor and repeated the test and got a reading of 140psi. Repeated immediately and got 130psi.

Is there any reason why the first reading is higher than the 2 that immediately followed it? Does using the adaptor with its longer thread make any difference?
Also, I forgot to open the throttle when I cranked the engine over (6 cranks each test). What difference, if any, to the readings would that make?

BTW, #2 read 140 then 135, #3 read 128 then 128, #4 read 140 then 135 all with the throttle closed.

Clan · Nov 2nd, 2007, 19:31

Those figures are reasonable but to get the proper figure you need the throttle wide open at all times when doing a compression test .

nejones · Nov 3rd, 2007, 11:22

OK, problem solved.

Thanks for all your help.
It turns out the green wire on top of the #1 injector had come loose.
Made a firm connection and cars running ok again when warm but has a slight problem when starting. It seems to die down to 300rpm when first started then after a couple of seconds it increases rpm.
Is it just the ecu still learning the new cam and head?

Clan · Nov 3rd, 2007, 13:26

Great news ! The dip in idle speed is either the throttle body/butterfly blocked with carbon when shut or it is incorrectly adjusted . A good test of a correctly set up and clean throttle is to clamp the hose going to the idle speed control valve and the rpm should drop from 900 to 600 or so and keep running , if it stalls it means there is not enough air flowing through the closed throttle body ..

Nov 2nd, 2007, 19:19	#1
nejones T-7 creator/driver Last Online: Jul 21st, 2012 22:26 Join Date: May 2007 Location: tipton View Photos By: nejones	Injector Q? and compression test questions Just a couple of questions really. 1990 760t b230ft - what type of fuel injector (make, model etc) is fitted on this car? Did a compression test today on the above engine. First time i've done a compression test so bear with me here please! Removed all the plugs and isolated the coil. I wound the tester into #1 without using the 'solid' adaptor on the bottom of the tube (the adaptor has a longer thread than that on the end of the rubber tube). I got a reading of 150psi. Then I used the adaptor and repeated the test and got a reading of 140psi. Repeated immediately and got 130psi. Is there any reason why the first reading is higher than the 2 that immediately followed it? Does using the adaptor with its longer thread make any difference? Also, I forgot to open the throttle when I cranked the engine over (6 cranks each test). What difference, if any, to the readings would that make? BTW, #2 read 140 then 135, #3 read 128 then 128, #4 read 140 then 135 all with the throttle closed. __________________ Cheers Nathan

Nov 2nd, 2007, 19:31	#2
Clan Experienced Member Last Online: Yesterday 22:41 Join Date: Jun 2007 Location: L/H side	Those figures are reasonable but to get the proper figure you need the throttle wide open at all times when doing a compression test . __________________ My comments are only based on my opinions and vast experience .

Nov 3rd, 2007, 11:22	#3
nejones T-7 creator/driver Last Online: Jul 21st, 2012 22:26 Join Date: May 2007 Location: tipton View Photos By: nejones	OK, problem solved. Thanks for all your help. It turns out the green wire on top of the #1 injector had come loose. Made a firm connection and cars running ok again when warm but has a slight problem when starting. It seems to die down to 300rpm when first started then after a couple of seconds it increases rpm. Is it just the ecu still learning the new cam and head? __________________ Cheers Nathan

Nov 3rd, 2007, 13:26	#4
Clan Experienced Member Last Online: Yesterday 22:41 Join Date: Jun 2007 Location: L/H side	Great news ! The dip in idle speed is either the throttle body/butterfly blocked with carbon when shut or it is incorrectly adjusted . A good test of a correctly set up and clean throttle is to clamp the hose going to the idle speed control valve and the rpm should drop from 900 to 600 or so and keep running , if it stalls it means there is not enough air flowing through the closed throttle body .. __________________ My comments are only based on my opinions and vast experience .

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