No fuel to CIS

[doopsx3]

I have a 87 Cab that has been sitting many years and I was told "ran when parked"...after cleaning the fuel tank and replacing the in tank pump I bench tested the main fuel pump and it proved good. My problem is the fuel pumps will only operate after the engine has been cranked over and then only for a short time. I know that the fuel pump relay senses the rpm signal to tell the pumps to continue to operate but aren't the pumps suppose to turn on when the ignition is initially turned to the on position and during cranking? Why would my Cab be doing this...

[Briano1234]

Upon first key in to the run the fuel pumps should cycle for 4 seconds to prime the system.
They are feed the run signal off the Coil. Which in turns runs the fuel pump relay.
every time a cylinder if firing the fuel pump will cycle.

If you are not getting the 4 second prime at key in to the run position
Suspects are the Ignition switch.
Fuel pump relay.

The Starter side of the ignition switch also powers the Fuel pump relay.

[doopsx3]

Thank you I will try the horn relay swap for the fuel pump relay temporarily to see if that fixes the issue...if not I will check the ignition switch...

[doopsx3]

the relay horn relay swap worked and what actually happened was the main fuel pump failed....replaced with a new Bosch unit and now I have fuel to CIS but unfortunately I have cold start issues

[Briano1234]

Look at the Warm up regulator, and or the cold start injector.
Timing could be off, and of course the o2 sensor...
You could try unplugging the o2 sensor to see if it is the issue, as unplugged it will force the engine in to closed loop.
If your Duty cycle is off that too, then there is the ubiquitous vacuum leaks.

[doopsx3]

only a billion things ...lol....new Bosch O2 sensor is installed.....cold start injector is getting required signal...timing is spot on

[doopsx3]

I just touched the 3mm allen screw adjustment for CO and the dang thing started and ran fine....letting engine cool down bit to see if it will start again

[Briano1234]

Probably what it was......
I can't remember if that screw has a o-ring.

[doopsx3]

not the air adjustment screw on the back of the plenum ...but the one next to the fuel distributor...the one you adjust when your setting the CO levels.....unfortunately now I can't get it to idle down unless I adjust that screw to where it won't start back easily....idles around 12-1400 rpm

[Briano1234]

That may be a timing issue, as the co2 was mis-set to accommodate for duty cycle adjustments or timing that was off.
I would first do the static timing to validate that all the marks are set, then adjust the duty cycle.

[doopsx3]

Timing should be spot on....I replaced the timing belt and did an ignition timing check afterwards but will check again....what do you use to check duty cycle....and how....dwell meter???....thanks for your help

[Briano1234]

Kammy has a how to at www.cabby-info.com

Duty cycle is a reverse of Dwell, but Kammy lists both I believe.
Also Harbor Freight sells a DVOM with Dutycycle and dwell.