shouldn't the green/white wire from the ECM be hot to "energize" the relay when the key is turned on ??? I cut the case off the relay, and If i manually press the contacts, the fuel pump will come on, so it leaves me to believe the ecm is not sending current to turn it on. Opinions ?? Thanks
The fuel pump fuse is definitely wired "hot". It's why a stuck oil pressure switch will turn your battery into a doorstop. I rewired mine at the fuseblock. Haven't had a dead battery due to a fuel pump running, in years.
Some people will recommend against doing this, for current capacity reasons, but it's never caused me a minute's trouble.
Edit - I believe that Terminal G on the ALDL is the fuel pump enable line. If you run 12 Volts to it, even with the key off, I'm pretty sure the pump will run. I don't know which side of the relay it connects to, however.
[This message has been edited by Raydar (edited 11-30-2018).]
FP Relay is Hot all the time on FP contacts. Yes, that and other things can ruin a battery fast. And ruin what even like the FP itself in this case. ALDL G is wired after the relay to tell if relay works or to power the FP to drain the tank etc.
Rewired fuse box is an iffy idea... I switch already handles a lot of power and FP needs 7-10 amps more. Iffy I switch can cause low volts and kill anything run by it. Pushing the switch to handle more power often only makes worse problems and sooner. See my Cave, Electric Motors
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
what I Have is full time power to both the oil sender and the relay. the relay will NOT turn on the fuel pump, but the oil sender(which I'm almost sure is bad) keeps it running constantly as long as the battery is connected.. I cut off the case of the fp relay, and if I push the Contacts closed, the pump runs. but, SHOULDN'T the ECM supply Power Through the green white wire to energize the relay >because the green white wire is doing Nothing, key on Or Off. I AM changing BOTH the oil sender And the relay, so I'll see if that helps the situation. Thanks
ECM switches to ground to turn on most relays etc. but in FP relay case, ECM switches Power to Dr Grm/wht wire. If no start/run then ECM turns that off after ~ 5 sec. if started after then turns on the relay again.
If has AC, just switch relays. Both are same. If you never get power to dr grn/wht wire then ECM or plug to it have problems. "Dead" ECM commonly seems to run but 1 circuit is dead from solder crack(s) etc. Even if you could find a crack joint and fix it... you very likely won't fix the ECM because you fix 1 and isn't the bad one causing the issue at hand this day.
OP sender is bad to run FP w/ engine off. Better is just upgrade 87 and older cars to 88 sender. See my Cave, Oil Sensor
OK, tried for "power" at #3 clear at ECM, I have power for 2-3 seconds when key is turned on. And power At the relay for 2-3 seconds. But the relay will Not "turn on" the pump. I've tried 5 different "Used" Relays,... nothing. will get a NEW Relay tomorrow.
Originally posted by theogre: .... Rewired fuse box is an iffy idea... I switch already handles a lot of power and FP needs 7-10 amps more. Iffy I switch can cause low volts and kill anything run by it. Pushing the switch to handle more power often only makes worse problems and sooner.
Mine has been that way for several years, with no problems. If I were using a high capacity pump, I might re-evaluate the decision, however.
IT PRIMES, then it" cranks" Until it has about 20 PSI of "OIL PRESSURE", then will start. it holds 50 PSI of "fuel pressure" as soon as the key is turned on, and never drops a pound after shutting the key off. The only way it will "Start" without" cranking it for 20 seconds" or so , is to give it a shot of" Quick Start", at which point it starts Immediately. If it "HAS Fuel Pressure", WHY will the Injectors,NOT INJECT, until the Oil Pressure goes up ?
So ALDL G is off too (Test light from G to Ground) ? ECM is likely bad or have other wiring problems.
Iffy parts/connections to/in the distributor and rest of ignition can cause fuel problems because ECM can't reliability see them or ECM internally has same issue. Pull Tach Filter and check rest of HEI. See my Cave, HE Ignition and Ground "Myth" notes
With the tach "strangeness" you mentioned earlier(other post) I would also check for a tach filter issue as Ogre suggested. On my 3800, I am not using a filter for the tach. The tach is driven off the white wire from the 3800 module. You are going to need to use your noids you mentioned, and check for injector pulses while cranking. Something is odd here. Especially if it will run good after an Either shot. PCM controls the negative side of the injectors. Unless the positive side is being drawn down someway. Did you check the injector wiring to make sure someone didn't wire them to the oil pressure sender during the swap. I know it sounds off. Sounds like you need to carefully review the wiring diagrams I posted before. Make a check list and go over all of them. Concentrate on Phonedawgz.jpg. Very good swap diagram. This also shows how to bypass the oil sending unit. This shows what has to modified on the 3800 harness. The rest of the wires, that don't show connections are ones that don't need to be modified on the 3800 harness.
[This message has been edited by cmechmann (edited 12-28-2018).]