OPS fixed, now hard start

[dieseldaver]

Hi all,

There's always something, isn't there? This past weekend, I put in a new Oil Pressure Switch, and it seems to be operating properly, the lift pump is working fine, and I can hear it switching off properly after shutdown. Only one problem. Since I fixed it, I seem to be having problems starting. It used to roar to life immediately, but now it takes some spinning of the starter, barely catches, and then comes up to idle. Could these items somehow be related? Or do you think its just coincidence that it started immediately after I fixed the OPS?

[ucdavis]

I can't see a relationship (doesn't mean one doesn't exist, just that I can't see it). OPS comes into play after engine oil pressure comes up so starting problem shouldn't involve OPS.
Fuel on start-up is controlled by Fuel Relay, then OPS takes over. Relay may be bad?

[dieseldaver]

I couldn't see any connection either, just thought I'd check.

Any way to check a relay? I know that I've seen previous posts saying that you should know how to check them because the schematic is on them, but forgive me, I'm not that great at electrical stuff. Can someone walk me through it?

[ucdavis]

Remove the relay & look @ the schematic. Two of the spades should be 12V that run the relay (i.e. closes the contacts, acting as a switch, to allow electricity to flow thru the other contacts).
Run 12V to the two indicated contacts, then check the other pair for continuity (w/12V & w/out). If the switched contacts are not infinite ohms w/out 12V to the control pair & zero ohms w/12V, then relay is busted.
Another approach is to buy a new relay (about $12) & try it.

[charliepeterson]

Another way is to look at the side of the relay for the schematic.
IIRC
ignition power to #86
ground from #85
battery power to #30
switched 12 volts down to the lift pump #87
nothing happens on #87A

[dieseldaver]

Thanks guys, I'll check it out over the weekend.

[Kollin Syverson]

Dave, I am still having somewhat of the same problem. I installed a relay between my OPS and lift pump which took care of my hesitation (because lift pump was not working). Truck starts up great and runs fine, but I still have no lift pump operation during cranking. I was under the impression that if you turn the key to start with tranny in gear(so engine wont actually start) you should hear lift pump running. I have since replaced my OPS and a new relay and fuse is good, still my lift pump will not function while cranking. There must be another fuse or connection somewhere that is bad. I will keep you posted if I find anything.