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sprinkles08
sprinkles08, ASE Certified Technician
Category: Jeep
Satisfied Customers: 21601
Experience:  Chrysler/Dodge/Jeep Master Certified, ASE Master and Advanced Certified, Trans and Hybrid Specialist
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ASD relay has ground on cavity 85 when ignition switch is in

Customer Question

ASD relay has ground on cavity 85 when ignition switch is in the OFF position, has no ground in the run position for 3 seconds initial pump prime.
Submitted: 9 months ago.
Category: Jeep
Expert:  sprinkles08 replied 9 months ago.

Hello and welcome to JustAnswer!

The fuel pump is powered by the fuel pump relay rather than the ASD relay. If there was an issue with the ASD relay then you'd be missing spark. If you're missing spark as well as fuel pump operation and the problems started at the same time then odds are the engine controller is not awake.

Are you only missing fuel pressure, or spark also?

Customer: replied 9 months ago.
BACKSTORY: i bought this cherokee from a guy who said it used to run fine then one day it just would not run anymore. He replaced the crank sensor, the cap/rotor , plug wires , plugs, ignition coil. When i bought it from him he said he thought it may be the computer so he found a replacement which i found to be a 1994 model ecu after research however obviously he gave up when this ecu did not do the trick, so i went and bought 2 additional 1991 ecus from the salvage yard to rule that out, i also have the original ecu.The 1991 ecu did nothing to remedy the problem. He also mentioned his battery would never hold a charge (which i found to probably be a bad alternator ground because it seems to charge now) he also mentionedPersonally i have replaced the entire distributor with a new camshaft position sensor inside of it, spark plugs, ecu as mentioned, crank position sensor, upgraded the cap and rotor, plug wires, i replaced the ignition coil since he did also but i know parts are bad out of the box sometimes. checked fuel pressure (31 psi at idle w/vacuum on-when it does start and run but you have to hold the throttle manually since its not hitting on all cylinders) fuel pressure is 41psi at idle with vacuum removed. fuel pressure stays steady after ignition turned off. Fuel injectors do pulse when i can get it to idle/run by hand -tested with noid light. I replaced the fuel filter and some old fuel lines and cleaned up the fuel system with seafoam for good measure.I also checked for voltage on the ignition coil wires, sometimes i get battery voltage sometimes not so much. Sometimes i get a decent pulse at the negative terminal of the ignition coil. tested with a test light, and with a noid light and with a multi meter with both the plug into the coil and backprobed and with the plug out just going straight into the female end of the plug.I have been working on this jeep for about 3 weeks now and have learned how the system is supposed to operate for the most part, which is why i started investigating the ASD/FUEL PUMP relays. I get battery voltage to the cavity 30 of these relays as i am supposed to full time because this is the battery full time feed, i get switched battery voltage at cavity 86 like i am supposed to because this is the ignition switched power cavity, the only cavities left after that are cavity 87 which is what the relay actuall powers ( in this case fuel pump relay powers fuel pump, asd relay powers injectors, coil, alternator that i know of) and we have the cavity that i suspect to be faulty, cavity 85 the control from ecu cavity. The fuel pump relay is supposed to get switched ground from the ASD relay ( the incoming ground control wire goes the the asd and jumps to the fuel pump relay) on this particular model and the ASD relay is supposed to get switched ground from the engine controller or ecu which switches that ground on for 2 to 3 seconds when the ignition is turned to on to operate the relays.And no, we either have no spark or weak spark...and it started out as very weak spark that was only enough to run 3 cylinders sometimes 4 cylinders. The fuel pump still primes which seems extremely odd as if something besides the fuel pump relay is supplying it with ground. I think what is happening here, is the cavities of the fuel pump/ASD relays have everything they are supposed to on all of the relay cavities besides cavity 85 which is getting full ground with ignition switch off. confirmed by taking the red test lead of a multimeter and placing it on the batterys positive post and my black test lead to cavity 85 of the asd relay OR fuel pump relay. When you turn the ignition on, your voltage between the two points drops to .5 volts or 1/2 of a volt Which, if im thinking about this correctly means that you get an extremely weak ground on cavity 85 with the ignition on and a good ground with the ignition turned to off. which to me, would be the reason i get either a weak spark or no spark at all but the fuel pump still primes even with a weak ground.I have 4 different ecus, they ALL do this. So i have ruled out the ecu as the culprit.The asd/fuel pump relay control wire is blue with yellow tracer which runs from the ecu about 2 feet then splices and runs back to the DLC next to the ecu then from that splice continues on straight to the power distribution center to the fuel pump/ ASD relays. I have clipped the asd/fuel pump relay control ground 2 inches from the ecu and 2 inches from the power distribution center to rule out that voltage was entering the line through a chafe rubbing the ground on a voltage line and nothing changed.Which lead me here to a chrysler expert, because to me, this seems to be a dead end UNLESS there is something that could be telling the ecu to reverse that ground path through the ignition switch or something. I want to point out that someone has replaced the steering column with a junkyard pull and there is the possibility that they did
Customer: replied 9 months ago.
something wrong there. BUT because the ecu controls the ground to these relays, i do not see how a faulty or backwards ignition switch could cause ground at the wrong time to the relays. Which is why im here, im fresh out of ideas, and i feel i am at a dead end.
Customer: replied 9 months ago.
when i said i clipped the control ground at the ecu and the pcm, i didnt mention this, but ofcourse what i meant was i ran a new wire 2 inches from the ecus plug to a point 2 inches from the power distribution center to rule out a short.
Expert:  sprinkles08 replied 9 months ago.

You don't have a fuel pump issue then, only a loss of spark?

Customer: replied 9 months ago.
that is true. Fuel pump seems to be working just fine.
Expert:  sprinkles08 replied 9 months ago.

Do you have a scan tool?

Customer: replied 9 months ago.
no i do not. sorry for the lag in response i did not realize your responses would be so fast. I will stay right here for the conversation from now on.
Expert:  sprinkles08 replied 9 months ago.

If you remove the relay and apply power to pin 87 does theengine sstart?

Customer: replied 9 months ago.
no, very good point though. I guess we now know the relay ground is not the main problem.
Customer: replied 9 months ago.
ok, i just went out and re tried jumping 30 to 87. I got a surprise. it started and ran horribly, so apparently my initial answer of no was because of bad memory so disregard that.Yes it starts jumping 30 to 87. When i did this i shut it down, i measure voltage from the battery negative to the coils plug on both wires, here are my results.With jumper in place instead of relay. Green wire gets 12.4 volts, grey wire gets 11.98 volts.with relay in place - green wire gets 0 volts, grey wire gets 12.4 volts
Customer: replied 9 months ago.
that is with the coil primary plug pulled off going straight into the female plug, this is not backprobing with the coils plug on the coil.
Customer: replied 9 months ago.
oh yes, this is with the ignition on and the vehicle not running forgot that detail. i took no measurements with it running. should i backprobe the wires and take measurements?
Customer: replied 9 months ago.
backprobed both green and grey wires on the ignition coil plug now, have 0.3 volts across the two. Im trying to get a reading across them while running, and a reading of each alone while running but my starter solenoid seems to be crapping out from all the starting attempts so i will wait a few minutes until it cools back down then try to get those. Im trying to be as helpful as possible with the limited automotive electrical knowledge that i have.
Expert:  sprinkles08 replied 9 months ago.

Have you checked for fault codes at least with the key cycle method?

Customer: replied 9 months ago.
12,35,55 fault codes are not much help unless theres a short in the fan relay or iac circuit. 35=fan relay OR iac
Expert:  sprinkles08 replied 9 months ago.

Do you have an incandescent test light?

Customer: replied 9 months ago.
i have one. Also, at this point i need to ask your opinion on the crank position sensor. Even though it has been replaced twice , they were chain parts store parts not oem jeep/chrysler parts. I had someone turning the key besides me finally to try and start this thing . (because it was getting hard to start and now wont start back at all) and i am almost certain that when it tries to start now that everything is somewhat warm that exact split second is when i hear my fuel pump kick on.Is it possible for the crank position sensor to be working intermittently giving fuel and spark? what would one check if they wanted to check that out.
Customer: replied 9 months ago.
i wish i could edit my responses instead of having to correct myself every time but anyway...what i meant to say was it was getting hard to start and now wont start back at all like it initially did earlier, and when it does almost catch, when you keep cranking and cranking and for just a second it pretends its about to start, i am almost certain that at that point i am hearing my fuel pump kick on.So, maybe my asd function is fine, maybe my ignition system and wiring are fine, my ecu is fine, MAYBE an aftermarket crank position sensor is causing these things not to work correctly because of mis reading, skipping reluctor wheel windows, etc. or maybe the crank sensor wiring is bad or anything in between related to the crank sensor.I know im all over the map on this , but truthfully i think were coming to a conclusion here.
Expert:  sprinkles08 replied 9 months ago.

Aftermarket sensors very often cause repeat issues which will make diagnosing it harder because you don't know if you're still fighting the original problem or compounded problems because of the replacement parts. Checking the cam or crank signal accurately would require a labscope. Usually the sensors will create a signal but it isn't a clean square wave like it should be.

Using the test light do you have power on one wire at the coil when cranking, and is it as bright as if connected to the battery?

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