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85 720 4x4 - Starting problems


PaddymanChris

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Hi mates,

This is my first post, but I've been lurking here for a while using some of your guys' advice quite often since I purchased my 85 pickup. It only has 83,000 miles on it (been sitting for a while with the guy I bought it from). Recently, it has started to struggle with starting in the morning. Here is a video of what it does...

 

 

Since buying the truck, I've replaced the spark plugs, ignition wires, ignition rotor, distributor, and battery. I've also replaced all the vacuum lines with new ones. I'm not sure if this is a starter problem or what. It only struggles if it's been sitting overnight or for a long while. I start it for work in the morning and it struggles, then on my lunch break it starts just fine, and when I leave for home it usually starts just fine.

 

I'm pretty new to working on cars, but I'm really enjoying tinkering with this thing. It runs beautifully when it starts and runs, it just struggles in the mornings. Oh, and I live in Utah, and it's been getting pretty cold in the mornings, so that may be contributing to the problem. Any advice for a beginner like me? Any would be greatly appreciated!

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Hi mates,

This is my first post, but I've been lurking here for a while using some of your guys' advice quite often since I purchased my 85 pickup. It only has 83,000 miles on it (been sitting for a while with the guy I bought it from). Recently, it has started to struggle with starting in the morning. Here is a video of what it does...

 

 

 

Since buying the truck, I've replaced the spark plugs, ignition wires, ignition rotor, distributor, and battery. I've also replaced all the vacuum lines with new ones. I'm not sure if this is a starter problem or what. It only struggles if it's been sitting overnight or for a long while. I start it for work in the morning and it struggles, then on my lunch break it starts just fine, and when I leave for home it usually starts just fine.

 

I'm pretty new to working on cars, but I'm really enjoying tinkering with this thing. It runs beautifully when it starts and runs, it just struggles in the mornings. Oh, and I live in Utah, and it's been getting pretty cold in the mornings, so that may be contributing to the problem. Any advice for a beginner like me? Any would be greatly appreciated!

Have you checked the battery? Sounds like maybe it's starting to get weak. Any auto parts store will test it for free in the truck.

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I replaced the battery with a brand new one since it started happening, but it didn't help the problem much. The battery it had was 15 years old!  Would bad wires or grounding be the problem? Or do you think it would be the starter? The fact that it starts some of the time and not others has me stumped.

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I replaced the battery with a brand new one since it started happening, but it didn't help the problem much. The battery it had was 15 years old! Would bad wires or grounding be the problem? Or do you think it would be the starter? The fact that it starts some of the time and not others has me stumped.

It could be the starter, couldn't hurt to pull and have it checked. How do the wires look going to the starter look? What motor do you. Have in it?

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do a load test on the battery and see if it can sustain the load that the starter puts on it (the starter draws a lot of current during cranking)

 

do voltage drops on the B+ and ground wires from the battery to the starter and vice versa (this will tell you if theres excessive resistance in the cables)

 

if that all checks out, pull the starter and have it tested, the brushes might be worn.

 

if that all checks out, then maybe a carb problem?

 

hope this helps. B)

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Clean the battery ground where it bolts to the intake near the top rad hose. Now clean and tighten the Positive cable where it bolts to the starter lug. I'll assume you cleaned the battery cables and posts at the battery. Are the clamps in good shape? Or are there screws it it to keep them tight??? Starters draw hundreds of amps and need solid connection.

 

 

 

Check the plug wires. With 8 of them it's easy to mix two up. Doesn't take much

720timing002Large.jpg

 

You don't mention checking or setting the timing. Pull the hose off the distributor and set the advance to 3 degrees.

 

One last thing... pull each coil wire and hold near ground. Is there spark when cranking on both or only one wire???

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  • 3 weeks later...

Ok, so a little update here. I spent all last saturday working on this thing, and found a couple issues. I took the passenger front wheel off to get to the starter easily, and noticed there was a bit of fresh oil on most of the wires and stuff around the area. After some further research, it looked like my oil pressure switch was busted, and was leaking oil all over. Took off the little rubber boot on the top, and there was more oil that came out. Didn't think it was good for oil to be coming out of the top of it where the wire plugs in, so I got a replacement and replaced it (which was surprisingly easy after taking the starter and oil filter out).

 

So, with the starter out, I took it over to autozone and had it tested. Everything was in the green, guy said it was running great. Now, I have read that these tests don't put a load on the starter, but I was glad to hear that it was running at least. While I was there, I bought a few new battery cables.

 

I cleaned the battery terminals (new battery so it wasn't too much), and took out the old positive and negative cables. I cleaned and wire-brushed where the ground bolted near the intake, and cleaned up the positive terminal on the starter. I installed the new cables and clamps, and reconnected everything. The only thing that had me kind of worried was the amount of oil that was on almost everything on the starter. There is a little wire connecting the larger and smaller parts of the starter that didn't have any protective coating on it, and it seeped oil out when I moved it slightly. Also, the little push-on wire to the starter was also covered in oil. Would those affect the starter working properly?
 

Anyways, got it all put back together, and it started great. It usually starts great, except after sitting for more than 8 or so hours. I checked the advance, everything looked good, and it looks like all of the plug wires are in the right positions. But, after all that, when I tried to start it monday morning for work, it was really sluggish like in the video I posted in the first post. Started great for the rest of the day, but come tuesday morning it struggled again.

 

My guess is that it's either a faulty new battery, or the starter. The fact that it starts great every other time makes me wonder though, I'm just stumped. Thanks by the way for the suggestions so far, I really appreciate the help!

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That sounds like you've got a short that's draining the battery when the vehicle sits for awhile, and then the battery gets charged up by the alternator when you actually run the vehicle.  To confirm/refute this: the next time you try to start the engine and it's not cranking well, pull out a multimeter and check the battery voltage.

 

Another option: shut everything off and remove the key.  Shut the driver door so that the cab illumination light is off, put your multimeter into current measuring mode and put it in series with the battery.  If the measured current isn't basically zero, you've got a short.

 

Note: if there is a significant amount of current, this could fry your multimeter.  I would only do this test on the fused port of the multimeter, and the port itself should show how much current it can handle (typically ~8-10A for fused, maybe up to 15A for unfused, and then sparks start flying).  If you do this test right, there's no real danger.  If something is still on that draws a lot of power (stereo?  lights?), then you might end up replacing that fuse.

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Connect a test lamp between a battery post and the cable. If there is a draw the lamp will light. If you have a clock option pull the #8 fuse over from the left hand side.

 

If the lamp lights, start pulling #9 through #15 till it goes out. This will identify the circuit with the draw on it. 

 

If it continues to draw there may be an after market amp, CB or CD player or car alarm still connected.

 

If still drawing pull the two wire plastic plug from the back of the alternator.

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When I got home from work last night I checked the battery voltages with the truck running and when everything was off. When running, I got a reading of 14.4 or so volts. When off, 12.67 volts. That sounded about right, but the real test was this morning when I checked it again. when I got out and tested it, it was 12.65 volts. Running, back up to 14.4. So luckily, I don't think the battery is getting drained over-night. Seems we had the same idea, because that would make sense with how it's starting in the mornings. Oh, and it started really slow again when I tried this morning. 

 

My next thought would be that the starter needs cleaning. I've only read a little about how and when to do it, so forgive me of my ignorance. Since the oil pressure gauge switch was leaking so much oil, I'm thinking that may have gummed up some components of the starter possibly? Have any of you taken apart and cleaned a stock starter on one of these? Or maybe that's not the right road to go down haha, I'm just stumped at this point (and I don't want to go out and buy a new starter just yet).

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It could also be wiring.  First and foremost, grab yourself a can of contact cleaner.  Something like this (this is just an example; there are plenty out there)

http://www.lowes.com/pd_172753-12704-40-610_0__?productId=3127949

 

Next, I would measure the voltage across the battery during cranking.  If that drops below 10V, the battery is a problem (the problem could simply be that the battery is too small for your vehicle, or that the starter is pulling more than the rated amount of current).  If you see low voltage at the battery, the wiring most likely isn't the problem (or, at least, it isn't the only problem).

 

Next, if it were me, I would use insulated alligator wires to try to measure the voltage across (that is, in parallel with) the starter while cranking.  With battery and wiring in good shape, you should not see the voltage drop below, say, 10V for any significant period of time (this is a guesstimate; I haven't actually run this test before).  If the connections leading to the starter (either hot side or neutral side) have high resistance, then those connections could cause a significant voltage drop.  The lower voltage at the starter means that the starter would require more current than normal to perform at its rated torque output.  Lacking that, it operates at reduced torque output (which could mean that it struggles to turn over your engine).

 

Given the sound from your video, I don't think it's the starter brushes (I could be wrong, of course).  It sounds like the starter is making less stall torque than required (stall torque meaning torque at ~0 rpm), and worn brushes would tend to cause drop-outs in the torque output, but would provide reasonable amounts of torque when the brushes are in contact with the armature.

This realfixesrealfast YouTube video has a couple demos of the kinds of noises you'll hear when the starter has different kinds of issues.  Even without the scope, the sounds are pretty distinctive:

 

 

Worst case, a starter is $20 at Pick-n-Pull.  Dunno what kind of stuff they have in UT, though.

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Why would the starter be slow in the morning and ok the rest of the day?

 

 

Tomorrow, connect jumper cables from  another battery or car. If it starts normally it's the battery you have... maybe bad or a hidden draw on it. If it is sluggish... maybe the starter.

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Here's what I found starting it this morning...

 

 

Seems the voltage dropped from about 12.4 to 9.9 when I started it up this morning. It started a little bit faster than it has been, maybe because it's a little warmer outside. Anyways, is that a normal drop while starting? Here is the battery that I have in it (1 month old)...

 

http://www.oreillyauto.com/site/c/detail/SSBG/24EXTJ/03321.oap?year=1985&make=Nissan&model=720%2BPickup&vi=1210374&ck=Search_C0423_1210374_3820&pt=C0423&ppt=C0005

 

Is that a strong enough battery for the truck? 875 cranking amps (700 in cold) seems decent enough to me, but I don't know. Does anyone happen to know the amperage pull from the stock starters? And Mike, as soon as I can get access to another vehicle I'll try that out. Thanks again guys for the help, I appreciate it a lot.

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Judging by the realfixesrealfast YouTube video that I posted, I think 9.9V is reasonable (you can see that for the healthy starter, the voltage drops to ~9.5V for his demo of a healthy starter).  I probably wasn't conservative enough in my estimate, but I trust that video more than I trust myself.  Additionally, the situation I dealt with was with a Miata race car, so the engine is probably just easier to turn over anyway (1.6L or 1.8L with low compression, vs. 2.4L for the 720)

 

Just to throw something out there, when was the last time the oil was changed?  Do you know what weight the oil is?  If it's too heavy (especially for cold temperatures overnight), that could theoretically cause it to be difficult to start as well.  Seems unlikely, but it's another guess.

 

I do know that in an extreme case, I dealt with a large diesel motor with oil that hadn't been changed in years and was literally chunky.  When we finally changed it (~20 quarts :D ), it turned over a heck of a lot easier.

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I've changed the oil every 2000 miles or so for the last few times, just to keep it clean. I changed the oil again last weekend when I replaced the oil pressure gauge switch that was leaking oil all over. I was using 5w-30 for the winter (very cold here in Utah). This last time though I figured I'd try the Delo 400 like some on here have suggested, and it's running great with it. I also was worried that it may be too thick, but starting-wise it's acting roughly the same as the 5w-30 was.

 

I'm thinking I may just take out the starter tomorrow, attempt to take it apart to see if the components are all gummed up or if it's just burnt out, and replace it with a new one if need be. I just can't think of what else it could be. Thanks again for your helpful suggestions, this community is great!

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My 85 does the same thing. I've done almost all the fixes that you have (battery, plugs, wires, starter, etc.) with no results. The only thing that I had done that seems to yield any sort of results was my timing. I had it set to the factory location (3 degrees before TDC) and changed it so it was dead center on TDC. It seemed to help it a great deal. Although, my engine wasted itself a few months later due to oil starvation (ate a rod bearing, wasn't pretty). I'll be watching and thinking about this. I can't play with my own since it doesn't have an engine so I'll try and live through you ;) I'll look for a video of mine doing that.

 

EDIT:

Here's that video. http://s303.photobucket.com/user/Nissan_Boy85/media/08ad1457.mp4.html?sort=3&o=10 I also just got to thinking. Engine's need 4 things to start and run. Fuel, Air, Spark and compression. Assuming your compression is good and in time, what if there was too much or not enough fuel? Like a stuck float? Heat causes things to expand, and the air temperature throughout the day gets warmer. If things expand enough to get "un-stuck".....not sure how I'm going to finish this. Just a thought.

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(Take this with a grain of salt).  I seem to recall someone on this or another forum who also had mysterious starting problems.  In his case, the problem was one of the electronic parts in the distributor, and when he replaced that, everything started working properly again.

 

Again, I don't recall where or when I read this, and my recollection of the problem could be mistaken.  But if you have access to a spare distributor, you might try swapping it in to see if that changes anything.  No promises.

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Pull both wires from the dizzy cap that go to the coils. Put a spark plug in the end or a screwdriver and place on or near a grounded surface and crank the motor over. Got spark from both coils?

 

YES... distributor and module is working.

EXHAUST COIL NOT WORKING... replace the #1 or far left hand side fuse in fuse box.

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  • 8 years later...

Hi, 

I was just reading this and want to reach out and let y'all know what my 1982 720 pickup is doing...

It was doing the exact same for most of the summer, really hard cracking, I rebuilt the carb( all nice and clean with me seals), it kept getting worse until now it won't start at all, doesn't even try there is no sound. 

I replaced the battery cables, cleaned the battery terminals, took out the starter, ( found the starter solenoid wasn't doing is job) got new starter and starter solenoid ( cheaper together) installed it, still nothing... 

I checked voltage all the way to the ignition.

Once I turned the key, the voltage dropped from 12 to 1.3 where the pins and the ignition cylinder come together.

I got a new ignition cylinder ( the truck drove for 3 times then did the same thing) 

I'm not sure where to start now but reading this thread, I'll change the oil... Work out from there...

Any other hints? ( There is no sound or any lights at all) I'm open to suggestions. It it my daily driver, if I can get her to and running once again... Thank you all!! 

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Is the battery fully charged?????????????????????

 

Find the fusible links that are on or near the positive battery post.

 

There is one Green link with a Red wire going into the harness. This is for the headlights. If headlights not working then power is not going through here.

 

There is a Black link that goes to the alternator and also the fuse box for things than need power without the ignition on such as brake lights, interior lights, clock and horn. Does your horn work. If it does then this link is likely ok.

 

There is a second Green link paired with the Black one. This sends power to the ignition switch.

 

I would say that there was nothing wrong with your starter or the ignition switch. All can be explained by bad connections at the fusible link(s)

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A short is power connected to ground. You would blow a fuse or have a fire. What you have is an open. Something unconnected.

 

Best thing is a test lamp. Touch both sides of the two fuses on the far right side of the fuse box. These connect directly to the fusible link. The test lamp should light, you don't need the ignition on for this. Pull the headlight switch to on and the relay above the fuse box should click. Headlights should come on.

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