Starter Replacement - Semi Realtime Help

[codertimt]

Hey guys, semi realtime because I won't be working on this any more tonight, but will be getting up tomorrow and starting again.

So, I began having the symptoms of failing contacts this past week, so I ordered up a Denso Rebuilt Starter and underwent replacement today. Seemed to be going well, no real problems thanks to the threads here.

Well, I buttoned everything back up and no start...So below I will list the symptoms and in the meantime I will search some no start threads for any ideas before going to bed. I haven't had a helper, so I haven't been able to listen to parts closely while someone else tries to crank...but from what I can tell...

• I believe I can hear the relay in the fuse box kick off...
• I do not think I'm hearing the solenoid on the starter kick off...
• 12.5 standing volts on the battery...and cranked fine right before starting.
• There is current draw in the cranking position...in fact it kind of acts like a dead battery or loose ground...kills all dash lights and what not...
• I can try to start in gear and there is no current draw in the cranking position...so not that.
• With manifold removed I jumped the solenoid directly from the battery and was able to get it to kick out the bendix...which should rule out dead battery or loose ground...
• Replaced with original starter and have same symptoms, so it doesn't appear to be actual starter...

So with all of that, it is appearing to me to be something is not allowing the ON wire for the starter solenoid to become hot. Either that wire got damaged in the harness somehow or something else in the system is causing no power to be sent...

• So, what are some possible reasons the computer wouldn't send power to starter?
• Does everything need to be hooked back up? After the first no start, I disassembled again to bench test new starter and I haven't been hooking everything back up to do initial testing...just setting on the manifold and hooking up the fuel lines. But symptoms have been the same when I hooked things back up the first time....unless I left some magic connector accidentally unhooked.
• Theft deterrent? Saw this on one Lexus troubleshooting site, tried an unlock/relock door with key procedure I tried without any change...
• ??????

Any ideas or troubleshooting methods would be greatly appreciated. I will try to get some help over tomorrow so that I can listen more closely....

Thanks
Tim

 

[ScubaJon]

my first guess is its the starter relay its in the large fuse block next to the stock battery, I would try taping it with the handle of a screwdriver a few times wiggle it around and then pull it out and clean the contacts if tapping with the screwdriver dont work. If thats what it is then you can get away with it a few times but its your warning to spend the 80 bucks on a new one because its on its way out.

 

[duggy]

my first guess is its the starter relay its in the large fuse block next to the stock battery, I would try taping it with the handle of a screwdriver a few times wiggle it around and then pull it out and clean the contacts if tapping with the screwdriver dont work. If thats what it is then you can get away with it a few times but its your warning to spend the 80 bucks on a new one because its on its way out.

If I read correctly above, he already replaced the starter.

@codertimt did it intermittently start before?

 

[codertimt]

If I read correctly above, he already replaced the starter.

@codertimt did it intermittently start before?

Yes, intermediate starting beginning last weekend. At 185K I automatically assumed starter contacts and ordered and installed replacement starter.

my first guess is its the starter relay its in the large fuse block next to the stock battery, I would try taping it with the handle of a screwdriver a few times wiggle it around and then pull it out and clean the contacts if tapping with the screwdriver dont work. If thats what it is then you can get away with it a few times but its your warning to spend the 80 bucks on a new one because its on its way out.

This is all I'm left with as being the cause. I left a pigtail on the small power wire on the starter and verified two things...

• There is no power getting to that wire when cranking with the key...
• I can jump that wire directly to the battery and starter engages...

So, everything points to it being the relay...it definitely clicks when turning the key, so I can only assume it's trying to operate, but shorted out inside and that is why all dash lights/etc go out when it engages...

 

[CharlieS]

On mine, AC and starter relay are identical, so you can swap them to troubleshoot.

 

[ScubaJon]

well if the ac and starter relay are the same I feel like a fool for spending 80ish bucks for the starter relay when the ac one is 12 bucks lol

 

[codertimt]

On mine, AC and starter relay are identical, so you can swap them to troubleshoot.

My starter relay is purple and explicitly labeled...I have been afraid to put another one in it's place for fear of frying it...

 

[CharlieS]

well if the ac and starter relay are the same I feel like a fool for spending 80ish bucks for the starter relay when the ac one is 12 bucks lol

I'm wrong.You are absolutely right! I stand corrected. Sorry.

I confused the magnetic clutch and mirror heater relays. I feel like a fool. Sorry.

 

[codertimt]

Well, I finally ran across the test procedure for the style relays I have and both starter relay and ACC relay(mentioned in starter section of 2004 FSM) test out okay, as would be expected since they clickety clack just fine...

I'm at a loss, I know there is alot more going on...it's not just a straight shot from the relay to the starter, rather it talks to the computer along the way...perhaps I've fried my computer(don't see how, did all work with battery unhooked)...perhaps I've knocked a wiring harness loose(can see this easy, I was climbing around the engine compartment like crazy...

Anyway, any wiring gurus have any ideas? Any Techstream expert know of anything I can look for there? I did a cursory glance and didn't see anything helpful or obviously wrong. I'll try it all at this point...

 

[Julian Stead]

Have you got a wiring diagram, if you have I prefer to carry out voltage drop checks for diagnosing this type of issue, a test lamp is also good tool. You test the circuit whilst it's under load not just surface voltage. I hope the relay does fix this but if you checked for a voltage drop across the relay you would be 100%.

Testing open circuit voltage with a multi meter will give you false readings as the resistance(voltage drop)takes no affect until the circuit is closed. This is why a test lamp is good as it closes the circuit and applies load.

Test the battery voltage when the engine is cranking not just the surface voltage. It shouldnt drop below 9v under load(engine cranking)

Sorry it's hard to explain how to do it but will explain more if your problem persists. You just need a wiring diagram to accurately diagnose it as you need to now what the pins in the relay do.

You test negative to negative or positive to positive to test voltage drop. The theory behind this is if you cut away half through say the main battery to chassis lead and carried out a resistance test it would read normal. If you check voltage under no load or minimal load it would read 12v as there is still enough cable for that current to pass but when you crank the engine you will get a voltage drop as not all the current can get through the cut cable, that energy will generate heat at this point, it's a hot spot in the cable. So you can read this voltage drop or bad connection by putting the black lead of multi meter on the negative on the battery and the red on the chassis bolt and read the voltage under load 0v being good 12v being bad as say you have a reading of 5v that will be the voltage drop in the lead. Max voltage drop is about 5%. You need a good battery to carry out these tests. You can test for voltage drop within a relay also using this method.

When I done my Master Tech training the only recognised form of electrical testing was either with a test lamp or voltage drop with a multi meter.

 

[codertimt]

100 Series Starting Wiring

• codertimt
• Jan 10, 2016

I have this from the 2004 FSM, I would think it would be pretty much the same...except the relay pinouts would be like below...

I used the following test procedure on the relays...

Only checks for continuity to see if the circuit closes inside the relay, which it does. So is it possible for the circuit to be completed but there to be almost no voltage making it across? I should be able to rig up a test for that. Similar to #3 above but also apply voltage to pin 1 and test the drop on pin 2...

As for testing voltage at the battery, I get no cranking at all so there is not voltage drop when turning the key to cranking position...well maybe .1 volts but nothing significant.

As for testing voltage drop otherwise...I know I can apply voltage to the starter solenoid directly(I still have a jumper wire attached) and the starter kicks in fine...so I would think the only wire in question would be the black wire in the diagram that appears to go from the relay directly to the starter...and as far as I can tell it's getting 0 volts on it when trying to crank(as tested on my jumper wire). So again that seems to indicate the relay isn't allowing voltage through even though it shows continuity or there is a continuity break on that wire between the relay and starter...

I will continue testing this afternoon and see if I can get any further data....

 

[Julian Stead]

Going by the top diagram if you make a small fly lead and link between pins 3 and 5 it should activate the starter as this bypasses the relay, you will just need to disconnect it to stop the starter from carrying on. The lower diagrams you link pins 1 and 2.

You can put a test light across pins 3 and 4(lower diagrams)and it should light up as bright as if you put it across the battery when cranking this will test the supply to the coil in the relay.

Test with a test light for a permanent supply to either pins 1 or 2 it is pin 5 in your upper diagram this is just like a switch so one side will have a permanent supply the other side just goes to the starter solenoid. One side of test light on battery Negative the other will probe the connections.

 

[Julian Stead]

Sorry just reread all of your posts, if you can feel the relay activating by put in your hand on it when activating this proves your coil side of your relay, this is the most important side as according to the drawings this will give you the most headaches diagnosing. So confirm this 100%. You need to be 100% before you move on when testing as this is where you end up going around in circles if you dont. And yes you can have continuity but little voltage getting through I wouldnt say 0 volts but very little. If the contacts are burnt then this is where the voltage drop can be. If the relay clicks and you do have voltage on either pins 1 or 2 then the fault is between the relay and the starter, if you then bridge out pins 1 and 2 and the starter turns over then the relay is at fault if there is no voltage at pin 1 or 2 check fuses.

You do need to be 100% on your battery though as I'm not sure your fly lead to the starter and having it turn over is proof that your battery is good as the starter circuit runs through the engine control module and if this does lose power like your dash lights due to a bad battery then you would lose the starter signal, which you bypass with your fly lead. So you could crank the starter with your fly lead and read your battery voltage. Use jump leads to mimic engine ground if in doubt on that. If your dash lights are affected then that is a sign of a voltage issue. Does the dash lights drop out when relay is removed and trying to start. If you test the battery voltage drop when cranking the starter at the starter motor itself then you could eliminate bad engine ground or a poor lead from starter to battery at the same time.

 

[codertimt]

JUst FYI, don't have a test light currently...need to add that to my arsenal...but I believe I have tracked down the problem with your help. Ran my additional tests...relay is a-okay. Voltage drop of .02. Found which pin socket in fuse box had permanent power and thus other side should be the one going to starter... Applied power to that pin socket with no result. So I believe I somehow managed to break that power wire while replacing the starter. Final test, I inserted my jumper wire into that pin socket and replaced relay...and the truck turned over with the key...

So yay, the problem is the wire from the relay in the fuse box to the starter...and boo that mean I have to once again dissassemble down to the starter in order to find where the break is, as I'm sure it's where I was manipulating the wires around the starter... Only good news, is I can do that in under an hour now...

Thanks for the help...

 

[Julian Stead]

On the top diagram there does look like there is a connector or something like that inline on that cable it's labeled ed1, there is no key provided to explain what it is, just glad it's wasn't on the coil side, that's where the fun would of began for you.

 

[codertimt]

On the top diagram there does look like there is a connector or something like that inline on that cable it's labeled ed1, there is no key provided to explain what it is, just glad it's wasn't on the coil side, that's where the fun would of began for you.

Yep, you and I are on the same wavelength...I just got inside from cleaning up. It's alive!!! In the FSM there is a page to reference that connector location. And I had enough sense to at least check that carefully before I tore the thing down again. Started looking around and found a grey connector hanging out of sight under the fuel filter. It plugs in right next to the fuse box and viola...a lot of time and work spend for a single unplugged connector. I don't know when or how it got yanked out, but something caught it and it did. And it couldn't have been any other plug...something unrelated to the starter...no, it had to be only thing that could be unplugged to make me thing the one thing on the truck that I had touched was in some way messed up. Oh well, she's starting and running again now.

Thanks again for all your help. I learned not to be afraid of wiring diagrams today. I shouldn't be, I had a digital electronics course in college...but that was along time ago...

100 Series plug to starter power

• codertimt
• Jan 10, 2016

 

[Julian Stead]

As you have diagnosed the issue I will explain how it would of been tested using voltage drop from start to finish, if at the beginning you put the negative multi meter lead on the Positive side of battery and the red on the live side of the relay switch it would read close to 0v, you had 0.2 which is good, then move it to the outgoing side of the relay whilst it is still connected to the fuse box, you just raise the relay up enough to get a probe on or manage to get under the fuse box to expose the connections, if this still reads close to 0.2 then that proves the relay is good, but when you move it to the starter cable your reading would of read 12v indicating an open circuit, you then move the black cable of the battery closer along the circuit, so say at the outgoing side of the relay then you would still get the reading of 12v. This proves your fault is between the relay and starter. If you then expose the wire about half way between relay and the starter and probe the cable, i have a special lead for this, it is like a bed of nails it squeezes onto the cable to test but leaves no marks when removed. If then you get a reading of 0v then you have gone past the fault, so you move the red lead back to that bed of nails and add another bed of nails half way back to the relay, if this reads 12v again then you have narrowed the fault down even further, so expose cable and repair. Hopefully you will find a connector between these points and test each side of the connector, which would be 12v, then reconnect connector and that would make it go to 0v. Now test the whole cable again from battery terminal to starter and it should turn over with a voltage of say 0.3v as it maybe slightly higher due to longer run. 0.5v is the max.

You can use this method to diagnose alot of electrical issues, it has the advantage over other tests as you are testing the circuit with its design current. So you can test main engine ground simply by putting the negative on the battery and the red on the engine block, crank the engine over and take your reading, you would expect it to be about 0.1 v due to it being a big short lead. Anything over 5% say 0.5v then clean the earth connections, if that doesnt improve it change the lead.

Glad to help, all the best

 

[wesquire]

Had my starter replaced and while still in the shop they couldn't get it to send power to the starter - took the manifold back off and checked all the connections. With a power probe they went through the bench test on old starter, the starter relay and contact points for the relay - were even able to send power to the starter with it but not with turning the key. Ended up being that the contact for the starter wire to connect to the fuse box was a little charred (their words) but the wire wasn't melted. They cleaned the contact point and the truck has started every time since. Hearing 'charred' immediately made me ask about risk of fire - was told that isn't a concern. Best guess is that when starter shorted out it sent power back upstream and it stopped at the relay since the circuit was open? Does that make sense? Anyone have similar experience? Any concerns about electrical fire?

I trust the guys, it just seems odd to me.

 

[wesquire]

So a little less than 2 weeks have passed and experienced the truck not wanting to start again after church. All dash lights and stereo come on, but hear nothing under the hood. Many tries later - after calling my bride to come pick up my daughter and me about to wrap up a call with AAA for a tow - it starts. Has started 5-7 tims since without issue.

Any ideas on the culprit?

First thought is it could be the starter relay, even though it bench tests fine when starter was replaced. Other would be whether there is something going on with the connection for the main starter wire to the bottom of the fuse box (see prior post) - assuming that would mean replacing the entire fuse box. Any chance a random
Ly flashing AC light that seems to only appear when it's hot could be related? Recall something in a post about that mentioning a magnetic clutch relay asa possible culprit. Just wondering if the common thread there is the fuse box they are all in. Haven't taken truck to see if the Refrigerant level is where it needs to be which is another possibility.

Thanks in advance - trying to avoid just throwing money at it randomly.