acceleration hesitation

1965-1971 Datsun 521 forums. All 520 and 521 topics and discussion can be found here.
netfreak
Posts: 23
Joined: Wed Dec 31, 1969 5:00 pm

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Alright i'm running out of ideas here. I'm having an issue where the engine hesitates quite badly when i accelerate. if i accelerate quite slowly it doesnt do it, but that makes driving in traffic a real pain. i had the carb tuned, accelerator pump replaced (which helped a bit as it was pretty much shot), new plugs/wires/dist cap and rotor, fresh oil. my next thing to try is playing with the timing but after that i'm clueless. any other ideas what it could be?


phiz
Posts: 54
Joined: Wed Dec 31, 1969 5:00 pm

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That's a good question that I'd like to hear some advice on, also.

My 620 hiccuped, farted, and passed-out last week and, I couldn't figure out...well, kind guess at, the problem until yesterday. It was starving for fuel. It would idle but, wouldn't keep running with the throttle open.

I checked the fuel lines and pump. Re-gapped the points and checked the timing. Tossed lots of combutable material down the carb's gullet. Threw chicken bones on the ground and did a medicine man dance. Nothing worked.

Tested the coil and found out it was shot. It wasn't sending juice to the solenoid relay thingy for the auto choke whatchamacallit. (I miss being able to pull a choke lever on the dash like a 521.)

Anyway, it runs now but, it's rough at WOT.

Here's where I need some opinionated advice: Should I rebuild the Hitachi or spring for the Weber 32/36 swap. Or perhaps some other fuel gulping combo?

~phiz

netfreak
Posts: 23
Joined: Wed Dec 31, 1969 5:00 pm

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If it wasn't for the cost of conversion and the increased difficulty in tuning, I'd ditch the hitachi. As part of my acceleration pump repair I had to buy a whole rebuild kit so one of these days I'm probably going to just rip it apart and go from there, otherwise I would consider other avenues.

I'm hoping to play with the timing tonight so I'll post up if it actually solved my problem. I've got an MSD ignition system and coil running great since I bought the truck so I don't imagine any problem on that end. I'm just *really* hoping that checking the gap in the dist and adjusting the timing will solve this.

netfreak
Posts: 23
Joined: Wed Dec 31, 1969 5:00 pm

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Turns out the gap in the dist was pretty out of whack. Did some quick adjusting and now there is no hesitation at all when i hit the pedal. It seems to rumble a bit more in the exhaust and the idle is a bit rougher. Advanced the timing a few degrees and it kind of helped but I'm going to re-gap it during the day when I'm not tired as hell. I'll also pay around a bit with the timing.

datsunexcells
Posts: 71
Joined: Wed Dec 31, 1969 5:00 pm

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netfreak,  When I pulled the pollution junk out of my first Datsun 521 Pick-up, I moved the ignition timing to TDC in order to get it to run right. The Chilton's Datsun Manual stated the the ignition timing was retarded 10 degrees, to accomodate the air pump and related equipment. I never had a problem with hesitation. Did you check for vacuum leaks?  John

netfreak
Posts: 23
Joined: Wed Dec 31, 1969 5:00 pm

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I'll have to take a closer look. The hesitation has come back. I'm in the middle of moving so it'll have to wait a few days or so before I can really put some time into this.

esodifferentia
Posts: 4
Joined: Wed Dec 31, 1969 5:00 pm

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[user=179]netfreak[/user] wrote: [quote]Turns out the gap in the dist was pretty out of whack. Did some quick adjusting and now there is no hesitation at all when i hit the pedal. It seems to rumble a bit more in the exhaust and the idle is a bit rougher. Advanced the timing a few degrees and it kind of helped but I'm going to re-gap it during the day when I'm not tired as hell. I'll also pay around a bit with the timing.
[/quote]
 

Yo.  Deciding to buy a '71 521.  The guy said it has a problem with acceleration and he couldn't find a vaccuum leak.  He rebuilt the engine himself and so if HE couldn't find a vaccuum leak, then I'm pretty sure thats not the problem.  Then I saw this thread and suddenly felt my seratonin level rise.

If you could, could you explain to me what gap you're referring to in the distributor?  And what kind of adjusting are you talkin about?

I play a lot of video games and have barely any mechanical knowledge.  The reason why I'm buying the truck is to start wrenching on s*** to get in touch with my inner man and learn myself some stuff.

Hoping you can help.

zetajunkie
Posts: 38
Joined: Wed Dec 31, 1969 5:00 pm

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i just put my  72 521 back together over the weekend, with a L18 w/ a 200sx  5 speed.  for the carb i used a rebuilt hitachi.  in 4th and 5th gears, i was getting the stutter effect, and eventually it just died.  the price of the damn NOS fuel pump was not worth the headache of having a friend bring me the old pump to where i was broke down (NOS pump stopped pumping).  with the old one on, i was able to get back to my work site.  it was still stuttering in 4th and 5th though.  thanks to my trusty parts truck, i replaced the crimped fuel inlet on the carb and added extra hose clamps to the tubes on the pump.  drove around great tonight. 

in the hesitation department, i figure making sure that all the fuel lines are sealed tight will help greatly, and make sure that there are no restrictions along the way (the hose clamps fixed any potential air leaks, and the other inlet didn't have a sharper bend than it needed)

zetajunkie
Posts: 38
Joined: Wed Dec 31, 1969 5:00 pm

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well, it's dying in 5th again... could it have anything to do with the wires that go into the transmission?  i know one of the sensors is for the backup lights, but what about the other one?  i haven't been able to find out what the lower sensor does... or what it is called, other then t/m switch (according to the wiring diagram).

any suggestions?

zetajunkie
Posts: 38
Joined: Wed Dec 31, 1969 5:00 pm

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okay, soldered up the tranny switches, realized since i'm using an pertronics ignitor inside my distributor i don't need to hook up the vacuum retarding sensor (right?)  back to square one...

71-521
Posts: 621
Joined: Wed Dec 31, 1969 5:00 pm

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if it had dual points originally there was a switch on the trans to activate the second set of points...usually not needed unless everything is stock and with petronics then I would assume it's not...so disco it!

zetajunkie
Posts: 38
Joined: Wed Dec 31, 1969 5:00 pm

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problem solved!  hidden fuel filter right off the gas tank, clogged....
replaced it, added new hose, better than new!

netfreak
Posts: 23
Joined: Wed Dec 31, 1969 5:00 pm

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Its hard to explain for me without diagrams. Mine is a single point distributor so when I pop the cover off, I see an adjustment screw in the top left quarter. It allows you to adjust the break point gap (if you watch the piece that moves when you loosen the screw, you'll see it)

[user=580]esodifferentia[/user] wrote
[quote]
Yo.  Deciding to buy a '71 521.  The guy said it has a problem with acceleration and he couldn't find a vaccuum leak.  He rebuilt the engine himself and so if HE couldn't find a vaccuum leak, then I'm pretty sure thats not the problem.  Then I saw this thread and suddenly felt my seratonin level rise.

If you could, could you explain to me what gap you're referring to in the distributor?  And what kind of adjusting are you talkin about?

I play a lot of video games and have barely any mechanical knowledge.  The reason why I'm buying the truck is to start wrenching on s*** to get in touch with my inner man and learn myself some stuff.

Hoping you can help.

[/quote]

netfreak
Posts: 23
Joined: Wed Dec 31, 1969 5:00 pm

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I might take a look into replacing my fuel pump and checking for other filters. I got the one in the engine bay already. It seems my hesitation problem goes away after some heavy driving (was testing a new intake setup in the middle of the night)

[user=418]zetajunkie[/user] wrote: [quote]problem solved!  hidden fuel filter right off the gas tank, clogged....
replaced it, added new hose, better than new!
[/quote]

esodifferentia
Posts: 4
Joined: Wed Dec 31, 1969 5:00 pm

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oh my lord.  Let me tell you!  Check it out, so the story starts a little somethin like this;

I make a right turn following my buddy to his house.  In third gear, my truck starts jerking when i gas it.   The rest of the way to his house, it keeps losing power until the engine eventually dies.

When we get to his house, i take off my air filter to notice that my butterfly is disconnected and the s*** is just dangling open.  So I reconnect it and i assume that its fine and try to drive it home.

It begins to jerk and die again, right when i get onto the on ramp for the highway.

CHP rolls up and asks me whats wrong with it (and this brunette CHP officer is phuxin fine as hell), and I tell her that its just dying.  So she calls the free towing company and what not.

When the guy gets there, instead of towing me, he takes off the fuel filter and points out a little bit of crap at the bottom of it.  He blows it out and connects it and asks me, "did you wait until about a quarter tank and fill it up all the way" which i did last night.  He said that there's bunch of crap that may be in your fuel tank since its an old truck thats gettin shot into my fuel filter and fuel line thats making the flow screwy which would result in the jerkiness.  After that, I was able to get it home, but still hesitates.

And this NETFREAK would make sense if there is a hidden fuel filter and hose that needs to be replaced.  He temporarily fixed it, but i have a feeling i'm going to have to phux with that other filter to get it workin better.

*hands you a beer* Take from this and drink from it.  This is a cup of my blood.  A cup of the new and everlasting gobstopper.

zetajunkie
Posts: 38
Joined: Wed Dec 31, 1969 5:00 pm

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i think whoever put the hidden fuel filter in my truck was trying to keep rust from the tank from travelling though the metal lines.   the crud at the bottom makes sense.  i had left a half a tank of gas in the truck during the 3 1/2 months i had it apart.  i didn't fill up right away either, so my case fits in with what mr. tow truck driver said....
if i can just find the time swap in my refurb'd tank...

esodifferentia
Posts: 4
Joined: Wed Dec 31, 1969 5:00 pm

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i haven't had a chance to look yet, but what you're saying is there might not necessarily be a hidden fuel filter in my truck?

as in someone was mickey mousin' your truck and through one in there specifically for all the crap in the gas tank?

as in, if i don't have a hidden filter, i'm going to have my gas tank cleaned out?

datsunexcells
Posts: 71
Joined: Wed Dec 31, 1969 5:00 pm

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esodifferencia,  Isn't there a drain plug on the bottom of your tank? It should help in getting most of the crud out of your tank. There should also be a filter in the banjo fitting at the fuel inlet on your carb. John

zetajunkie
Posts: 38
Joined: Wed Dec 31, 1969 5:00 pm

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eso, mickey mouse lived in my truck before i came into it possession of it.  i swear i have 3 different wiring harnesses under the hood, and parts of each are connected... hell, i'm glad that filter was there, it kept all that crap out of my freshly rebuilt everything (or at least it kept it from clogging the inlet on the carb)
if you're somewhat sure that there's debris in your tank, draining it would help (shouldn't take too long to do).  if time is of the essence, go grab yourself a nice $3.49 inline fuel filter and splice it in somewhere. mine is resting on the gas inlet tube just before the steel lines start. it took 10 minutes to put in, due to the multiple rusted hose clamps of different types that were never removed, just pushed back a bit to make space for the next one

70 521 project
Posts: 3
Joined: Wed Dec 31, 1969 5:00 pm

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I had the same problem with ny 521.  I thought that I hade done everything but I guess not.  I rebuilt the carb, replaced the distributor with a brand new one I bought from Baxters that was a 1980 electronic one. screwed with the timing and even went back through the carb.  While having the carb apart and not knowing were the jets were supposed to be a started switching them around and found the right combination and it ran ok but still was hesitating on acceleration.  I was watching the squirts from the accelerator pump and it was hardly anything, so I bent the linkage a little so that the plunger was forced back up a little more.  I found that the bushings in the accelerator pump arm were so worn that it was not allowing the pump to move positively.  This may not work for you but it did for me let me know if it does.

netfreak
Posts: 23
Joined: Wed Dec 31, 1969 5:00 pm

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Hmm.. might try giving that shot. I'm buying another vehicle in a couple weeks but i wouldnt mind having this run decently until then. My next problem is the exhaust broke in half and it sounds like a machine gun when i accelerate :)

[user=635]70 521 project[/user] wrote:
[quote]I had the same problem with ny 521.  I thought that I hade done everything but I guess not.  I rebuilt the carb, replaced the distributor with a brand new one I bought from Baxters that was a 1980 electronic one. screwed with the timing and even went back through the carb.  While having the carb apart and not knowing were the jets were supposed to be a started switching them around and found the right combination and it ran ok but still was hesitating on acceleration.  I was watching the squirts from the accelerator pump and it was hardly anything, so I bent the linkage a little so that the plunger was forced back up a little more.  I found that the bushings in the accelerator pump arm were so worn that it was not allowing the pump to move positively.  This may not work for you but it did for me let me know if it does.
[/quote]


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