need help with 30 amp fuse / asd relay

[tow_hook]

the short of it, my wife's 02 wj limited, with a 4.7

I changed the head gaskets a few weeks back. it's all together, idled ruff, (starts right up ) .. shut off and gave a code a p01389. 30 amp fuse was popped. replaced fuse, happened again.....

from moving the wires to the valley and back.. checked for shorts in the wires. notta no opens or out of limits... checked coils, injectors, sensors. notta..relays pulled o2 fuse, and sensors. same deal... pulled each coil and ran, no changed every thing is with in spec as per my d.c. service manual.. love that book

currently.... the jeep starts easy idles great cold, idle kick down no problem... after 8-10 mins stops running like the key was turned off the fuse doesn't pop in the p.d.c. ??? restart runs less time idles ruff, pops fuse will run 30 seconds - 2 mins

to narrow things downlast night ... a straight power line to the coils was run with 20 amp blade fuse, it will start and now popps that 20 amp fuse, on the ruff idle.. it popps as it is about to recover from the low...

last night also jumped the rear coil wire out of the (loom ) harness, not knowing was could be bad back there... same deal still shuts off...

is it poss to have 2 bad coils going to ground??

i've been chasing this for 2 weeks... any help would be great

for the whole story check here....
sorry i can't post the link to the whole story yet....

i've been to the dealer, and talked to KOLAK'S JEEP, and he also feels it is a electrical issue.. the engine purrs at cold idle, and rev's great... to scann too with live diag shows were are good there....

thanks brian

 

[spyder873]

here is the link to the build, I have been working on this with brian and we can't seem to track it down, we have gone over most if not all the wiring to look for shorts, loose grounds.etc. It has really been a pain in the ass,lol.any ideas would be greatly app.
thanks Fred

project twisted sister goes HO - Forums

what we might try is isolating two coils at a time to try to find the bad set.

we are not getting any trouble codes on the computer now... so it has kinda got us baffled

 

[SteelHeadz]

Trace the engine wiring harness around the engine cylinder head and see if a wire accidentally got pinched when you installed the cylinder heads. Did this symptom exist prior to the head gasket replacement?

 

[spyder873]

the problem showed up upon start up after the head was replaced. we have ohmed out all the wires to the different systems on that fuse, O2 sensors, ign system, fuel system. we opened up the loom on the passenger side and didn't see anything burnt or pinched. we bypassed the harness by going from 12v to the coils , at the time we installed a 20amp fuse in line with the coils and now it blows instead of the 30 amp.

The next step is to break the coils down into pairs with a fuse on each set of two to see if we can narrow it down even more.

When we checked the relays to see if they were in spec(50 to 80 ohms). we found 3 that were over, After replacing them, the engine would just shut off after about 5 minutes ,not blow the 30 asd fuse, When started right back up then it would blow the fuse.

 

[tow_hook]

Trace the engine wiring harness around the engine cylinder head and see if a wire accidentally got pinched when you installed the cylinder heads. Did this symptom exist prior to the head gasket replacement?

no problems before i did the heads, the rear loop was checked, but not opened,to check visualy... it does have slack.. i traced the loops from both heads, nothing feels or looks pinched...

but jumping the the power over the manifold it still shuts off... enven when the rear loop is out... so that would take the rear loop out right??? each coil does have a ground wire ... but it's suposed to ground... the 30 amp asd fuse had a hard short, and when it was tested for amps it didn't surpase the amp limit of 30 (tested when the engine stopped ) it looks to be a short to ground... but the coils and wires tested...

unless the coil is grounding, but each coil was pulled and the engine started 8 times, once for each out being pulled... so that should take it out of the problems unless there is more then one coil shorting, but what are those odds???

used coils are running 25$ esch and new 30$ i have a new coil... so if i fuse each coil, and see what pops??? right....:???:

 

[SteelHeadz]

Remove the ASD relay.What is the voltage of the fused battery+ circuit at the ASD relay connector? . If it's above 10.0volts you have a bad PCM.

 

[tow_hook]

Remove the ASD relay.What is the voltage of the fused battery+ circuit at the ASD relay connector? . If it's above 10.0volts you have a bad PCM.

did check that, and it tested... ( as per diag for code po1389, and p01388 )

the direct jumper to a 12 volt sourse ( for the coil power wire ) would have by passed that right??? that's why the 20 amp in line blade fuse popps now vs the asd fuse.... cause it's not going back threw the pcm or pdc....???

thanks for you help...

 

[SteelHeadz]

No, it could mean that the short to ground is in the ckt from the PDC to the PCM. Check and bypass the darkgreen/ lightgreen wire from the C3 connector of the PCM pin 12 to the PDC and see if that makes a difference. That's also the same circuit that goes to the coil rail which should be a darkgreen/orange wire then loops back to the PDC fuse 16.

 

[tow_hook]

No, it could mean that the short to ground is in the ckt from the PDC to the PCM. Check and bypass the darkgreen/ lightgreen wire from the C3 connector of the PCM pin 12 to the PDC and see if that makes a difference. That's also the same circuit that goes to the coil rail which should be a darkgreen/orange wire then loops back to the PDC fuse 16.

we checked pcm grey plug pin 12 to the pdc.., and got a ohms reading... if i recall it was in spec...

yes the dark green with orange tracer goes to fuse 16, that fuse is good, and has 10 amp draw to it when the engine is running but has never popped... that's why it seems odd.....???

 

[SteelHeadz]

What's the voltage on fuse 16?

 

[tow_hook]

What's the voltage on fuse 16?

umm have't checked that yet..... what affects would that have??? the amps is under 10 and it is a 15 amp fuse......... ohms x 12 = volts or amps.... errr never wanted to be a tech....

 

[SteelHeadz]

One foundational unit of electrical measurement, often taught in the beginnings of electronics courses but used infrequently afterwards, is the unit of the coulomb, which is a measure of electric charge proportional to the number of electrons in an imbalanced state. One coulomb of charge is equal to 6,250,000,000,000,000,000 electrons. The symbol for electric charge quantity is the capital letter "Q," with the unit of coulombs abbreviated by the capital letter "C." It so happens that the unit for electron flow, the amp, is equal to 1 coulomb of electrons passing by a given point in a circuit in 1 second of time. Cast in these terms, current is the rate of electric charge motion through a conductor.
As stated before, voltage is the measure of potential energy per unit charge available to motivate electrons from one point to another. Before we can precisely define what a "volt" is, we must understand how to measure this quantity we call "potential energy." The general metric unit for energy of any kind is the joule, equal to the amount of work performed by a force of 1 newton exerted through a motion of 1 meter (in the same direction). In British units, this is slightly less than 3/4 pound of force exerted over a distance of 1 foot. Put in common terms, it takes about 1 joule of energy to lift a 3/4 pound weight 1 foot off the ground, or to drag something a distance of 1 foot using a parallel pulling force of 3/4 pound. Defined in these scientific terms, 1 volt is equal to 1 joule of electric potential energy per (divided by) 1 coulomb of charge. Thus, a 9 volt battery releases 9 joules of energy for every coulomb of electrons moved through a circuit.
These units and symbols for electrical quantities will become very important to know as we begin to explore the relationships between them in circuits. The first, and perhaps most important, relationship between current, voltage, and resistance is called Ohm's Law, discovered by Georg Simon Ohm and published in his 1827 paper, The Galvanic Circuit Investigated Mathematically. Ohm's principal discovery was that the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage impressed across it, for any given temperature. Ohm expressed his discovery in the form of a simple equation, describing how voltage, current, and resistance interrelate:

In this algebraic expression, voltage (E) is equal to current (I) multiplied by resistance (R). Using algebra techniques, we can manipulate this equation into two variations, solving for I and for R, respectively:

Let's see how these equations might work to help us analyze simple circuits:

In the above circuit, there is only one source of voltage (the battery, on the left) and only one source of resistance to current (the lamp, on the right). This makes it very easy to apply Ohm's Law. If we know the values of any two of the three quantities (voltage, current, and resistance) in this circuit, we can use Ohm's Law to determine the third.
In this first example, we will calculate the amount of current (I) in a circuit, given values of voltage (E) and resistance (R):

What is the amount of current (I) in this circuit?

In this second example, we will calculate the amount of resistance (R) in a circuit, given values of voltage (E) and current (I):

What is the amount of resistance (R) offered by the lamp?

In the last example, we will calculate the amount of voltage supplied by a battery, given values of current (I) and resistance (R):

What is the amount of voltage provided by the battery?

Ohm's Law is a very simple and useful tool for analyzing electric circuits. It is used so often in the study of electricity and electronics that it needs to be committed to memory by the serious student. For those who are not yet comfortable with algebra, there's a trick to remembering how to solve for any one quantity, given the other two. First, arrange the letters E, I, and R in a triangle like this:

If you know E and I, and wish to determine R, just eliminate R from the picture and see what's left:

If you know E and R, and wish to determine I, eliminate I and see what's left:

Lastly, if you know I and R, and wish to determine E, eliminate E and see what's left:

Eventually, you'll have to be familiar with algebra to seriously study electricity and electronics, but this tip can make your first calculations a little easier to remember. If you are comfortable with algebra, all you need to do is commit E=IR to memory and derive the other two formulae from that when you need them!

• Voltage measured in volts, symbolized by the letters "E" or "V".
• Current measured in amps, symbolized by the letter "I".
• Resistance measured in ohms, symbolized by the letter "R".
• Ohm's Law: E = IR ; I = E/R ; R = E/I

 

[SteelHeadz]

I just noticed that the downstream O2 sensors also shares the same ckt to the PDC fuse# 16. check the O2 sensor wires for a pinch or rub through.

 

[tow_hook]

I just noticed that the downstream O2 sensors also shares the same ckt to the PDC fuse# 16. check the O2 sensor wires for a pinch or rub through.

ok so 10 volts is what i should have on fuse 16,

as far as the o2 sensors i did pull that fuse/relay and unpluged each sensor with out any change and restarted the engine 4 times.. and checked the wires.... notthing out of line...???

 

[tow_hook]

wow that was helpfull, i ran a shop as service manager.. and never really went deep in to the electrial side of things...

 

[tow_hook]

it's raining ,and getting late i'll check the voltage tomorrow..

thanks... i least i'm checking the right stuff so far...

 

[tow_hook]

thanks for the help, but as of today @ 3 it was trailered to the shop... I will post the answer to the problem.... i did take, or try to rive it up the street.. notta it went in to limp mode, and i had missfires on every cyclinder... so my bet is on the pcm...??? but who knows....

 

[SteelHeadz]

Keep us posted.

 

[tow_hook]

i got the call, from the shop... it looks like the crank sensor seems to the cause and has the coils on too long... and the coils are over heating... and shutting off.... there are going to swap a new crank sensor in it weds... and we will see.. if not the front cover might have to come off....

 

[SteelHeadz]

Do they have doubt's of the multiple timing chain setup?..