Stoffregen Motorsports Posted May 18, 2021 Report Share Posted May 18, 2021 But you agree that the pump is going bad, right? Then replace that and keep the rest simple. 1 Quote Link to comment
Crashtd420 Posted May 18, 2021 Author Report Share Posted May 18, 2021 Just now, Stoffregen Motorsports said: But you agree that the pump is going bad, right? Then replace that and keep the rest simple. Well since I removed the Holley regulator from the equation and I still have inconsistent pressure yes I believe the pump is going bad... The regulator might still be good but I actually like having the return line instead, I feel like this might help the pump live longer this time by letting some fuel circulate.... 2 Quote Link to comment
Charlie69 Posted May 19, 2021 Report Share Posted May 19, 2021 (edited) On 5/8/2021 at 12:49 PM, Crashtd420 said: No the 521 didnt have a return... I'm planning to use the 1/4 vent tube as a return input and I'm adding a vent line tee to what I believe is the filler neck overflow.... I'll setup a few tests and add an appropriate restrictor to the return line... The 521 did have a vapor check valve. There is a three hose fiting on the drivers side inner fender that pulls fuel vapors from the tank and the engine block to the air cleaner. Here is what I am talking about. Scroll down on this page and there is a complete explanation of how this valve works. http://datsun1200.com/modules/mediawiki/index.php?title=Fume_Control Edited May 19, 2021 by Charlie69 4 Quote Link to comment
Crashtd420 Posted May 20, 2021 Author Report Share Posted May 20, 2021 The datsun passed inspection today.... Ebrake wasn't an issue but they didn't test it like the dealership did, whatever it passed.... What surprised me was he actually checked if the windshield washer squirted.... glad I fixed that last week... The only other thing he said which was borderline was my right tire had a little movement but he said it will pass.... Apparently once the inspection starts cameras turn on but once they finish they automatically turn off.... So after they jacked it back up and wiggled the tire so I could have a look.... Tierods were all good and tight but I could see the idler arm move.... Guess I'll be ordering one of those this week.... Its probably one of the last untouched old parts on the truck.... 2 Quote Link to comment
Crashtd420 Posted May 22, 2021 Author Report Share Posted May 22, 2021 Well I installed a small ball valve and filter on the return line.... Valve acts like an adjustable regulator and filter always me to see the gas flow..... probably not neccessary but I like having the visual.... 1 Quote Link to comment
Crashtd420 Posted May 22, 2021 Author Report Share Posted May 22, 2021 I also started realizing how neccessary the bed is for carrying even small stuff.... After work I have all my stuff with me then I pick up my kid from school and he has all his stuff... the cab fills up quickly..... So I decided to ghetto mounted my trunk box so I have some storage and a locked box.... 1 Quote Link to comment
d.p Posted May 22, 2021 Report Share Posted May 22, 2021 So you’re just never going to put your bed back on? 1 Quote Link to comment
Crashtd420 Posted May 23, 2021 Author Report Share Posted May 23, 2021 7 hours ago, d.p said: So you’re just never going to put your bed back on? It needs to be stripped, have some small repairs done and get refinished... Probably wont happen till end of summer into the fall.... Trying to get some house projects finished up. I'm painting the kitchen cabinets and doors in my garage right now, and having countertops and floor installed in our kitchen. After that we are fixing up the porches, its an old house so we want to keep the old look.. the point to that is dustless blasting. .. the porches need to be brought down to bare wood because there are to many old layers of paint, to restore them properly i think dustless blasting would be the perfect starting point, plus I figure I'll get the truck bed done at the same time.... 2 Quote Link to comment
Stoffregen Motorsports Posted May 23, 2021 Report Share Posted May 23, 2021 Good idea. I've never seen the dustless blasting before. I assume they use different media for different surfaces...? 1 Quote Link to comment
Crashtd420 Posted May 23, 2021 Author Report Share Posted May 23, 2021 Some times you need to do what you have to do on a hot day to keep the kids cool.... 2 Quote Link to comment
Crashtd420 Posted May 23, 2021 Author Report Share Posted May 23, 2021 Just now, Stoffregen Motorsports said: Good idea. I've never seen the dustless blasting before. I assume they use different media for different surfaces...? They do, atleast that's what I have read.... I'll know more once I finally get them over for a quote.... 2 Quote Link to comment
Charlie69 Posted May 23, 2021 Report Share Posted May 23, 2021 Dust less blasting is done with water to control the dust. 1 Quote Link to comment
Crashtd420 Posted May 24, 2021 Author Report Share Posted May 24, 2021 I finally swapped the pump out this afternoon, I had 5psi when I got in the truck this morning.. I was at 2psi by the time I got to work.... When I went to go home I still had only 2psi and i even had the 1/4 returned line closed.... After the new pump was installed I had 3 1/2 almost 4psi, and I was able to use the valve on my return line to lower it to 3.... I'll check and see what i have tomorrow for consistancy.... 1 Quote Link to comment
Stoffregen Motorsports Posted May 25, 2021 Report Share Posted May 25, 2021 Voltage drop. What gauge wire are you using to feed the pump? It should probably be no smaller than 12ga if running the length of the truck. Are you using a relay to fire the pump? Or is the power going through a toggle switch? Check your ground too. 1 Quote Link to comment
Crashtd420 Posted May 25, 2021 Author Report Share Posted May 25, 2021 1 hour ago, Stoffregen Motorsports said: Voltage drop. What gauge wire are you using to feed the pump? It should probably be no smaller than 12ga if running the length of the truck. Are you using a relay to fire the pump? Or is the power going through a toggle switch? Check your ground too. I'm 99.999% pretty sure I have 12 gauge as the power lead and all my toggles do trigger relays and the grounds are solid... So far atleast these experiments have shown me that I did have a fuel issue causing my misfire... The one thing I noticed was the new pump is maintaining fuel in the filter where the other pump was not when trying to maintain a proper psi... I'll check before I leave work and when I get home to see what I have.... 1 Quote Link to comment
Stoffregen Motorsports Posted May 25, 2021 Report Share Posted May 25, 2021 Next test is to check the actual voltage at the pump when the pressure is low. Maybe your alternator isn't keeping up, or something weird like that. There are only a couple possible reasons for inconsistent fuel pressure. Voltage drop is the most likely, but plumbing could also be a factor. Did you ever install that return? Maybe that's causing problems. These pumps were not intended to be used with a return. Another possibility is the gauge. I had a truck in here a few years ago that had a similar problem and I finally figured out that the gauge was reading erratically, but the pressure never did drop at all. In plumbing, there is a hammer effect that happens when a tap is shut off and this can affect the reading, but not the actual PSI. 1 Quote Link to comment
Crashtd420 Posted May 25, 2021 Author Report Share Posted May 25, 2021 32 minutes ago, Stoffregen Motorsports said: Next test is to check the actual voltage at the pump when the pressure is low. Maybe your alternator isn't keeping up, or something weird like that. There are only a couple possible reasons for inconsistent fuel pressure. Voltage drop is the most likely, but plumbing could also be a factor. Did you ever install that return? Maybe that's causing problems. These pumps were not intended to be used with a return. Another possibility is the gauge. I had a truck in here a few years ago that had a similar problem and I finally figured out that the gauge was reading erratically, but the pressure never did drop at all. In plumbing, there is a hammer effect that happens when a tap is shut off and this can affect the reading, but not the actual PSI. I'll double check the voltage but I do believe that it is good.... The gauge is new a liquid filled.... I do have the return hooked which I can close off If i want..... right now its just barely cracked open and i removed that small filter..... I really dont know if I'm chasing an issue or creating a new one.... All I know is when I would get on the highway in the morning if I was to aggressive and running the rpm up by the time I got to 4th it would give me that miss fire.... then i let the fuel catch up and the issue goes away.... I haven't had that issue since I removed the regulator and added the return.... I guess I'll see how this new pump acts and go from there..... 2 Quote Link to comment
Crashtd420 Posted May 28, 2021 Author Report Share Posted May 28, 2021 So where I'm at now.... I did check the voltage and it is good .... So I have a new pump installed, still using the bypass just slightly open to allow gas to continuously flow through the pump and I reattached the pressure regulator under the hood.... Gauge is currently stable at 3psi.... I'll see how that behaves.... 1 Quote Link to comment
Charlie69 Posted May 28, 2021 Report Share Posted May 28, 2021 What does your pressure do running down the hiway at 65 mph? Quote Link to comment
Crashtd420 Posted May 29, 2021 Author Report Share Posted May 29, 2021 12 hours ago, Charlie69 said: What does your pressure do running down the hiway at 65 mph? No idea, cant see, its under the hood... . I can rev the motor in the driveway with no change to the psi.... I am able to see the filter, and i am noticing the filter is staying fuller ... before if I went full throttle I could see the filter empty and then refill when I let off.... I'm not seeing that now.... I'm thinking the old pump was just on it's way out , I'll know more if this solved what I was experiencing and seeing... 1 Quote Link to comment
Charlie69 Posted May 29, 2021 Report Share Posted May 29, 2021 You might consider a temporary fuel pressure gauge in the cab so you can monitor what the fuel pressure is doing throughout the driving experience. Up hill, down hill, normal acceleration, hard acceleration, stopping, is there any surging of pressure higher or lower. Quote Link to comment
Crashtd420 Posted May 29, 2021 Author Report Share Posted May 29, 2021 1 hour ago, Charlie69 said: You might consider a temporary fuel pressure gauge in the cab so you can monitor what the fuel pressure is doing throughout the driving experience. Up hill, down hill, normal acceleration, hard acceleration, stopping, is there any surging of pressure higher or lower. I'll see how this goes for now and keep that idea in mind if I need to deal with this further.... 1 Quote Link to comment
Crashtd420 Posted June 1, 2021 Author Report Share Posted June 1, 2021 Just turn 10000 miles on the odometer this morning..... 4 Quote Link to comment
Crashtd420 Posted June 8, 2021 Author Report Share Posted June 8, 2021 So I stopped looking at fuel pressure because it was driving me crazy. .. I'm not even getting into it... what I will say is I do believe either the pump was going bad or it was related to the fact that it was dead heading to the carburetor.... possibly both.... Since the new pump and adding the bypass, what I have noticed is that the misfire I was getting before is gone... I have also been able to add 4 degrees of timing to my full advance .. I have been running 15 at idle and i dropped the full advance to 28 thinking that was the issue... it never did go away... go figure since it was a fuel issue... so now I'm up to 32... So far so good.... Also recently replaced my idler arm... old one was borderline at inspection.... It did seem to tighten up the steering a little while driving so that's a win too.... 2 Quote Link to comment
Stoffregen Motorsports Posted June 8, 2021 Report Share Posted June 8, 2021 I know what you mean Neal. Fuel PSI tends to bounce around, for many different reasons. Sometimes the gauge will read high, sometimes low. It should steady out at full throttle, or even just when accelerating, but when at low throttle opening or at idle, it will fluctuate. There has to be a calculation based on volume and PSI, but I've never taken it that far. 2 Quote Link to comment
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