Engine runs a LOT worse with high HUMIDITY !

[sage691]

36 minutes ago, datzenmike said:

Can you post a picture of it? If after market it could have failed or be incapable of providing the quantity you need.

 

Well that leaves a volume test at the carburetor.  If over 1 liter per minute then the problem is perhaps at the carburetor inlet. There is a banjo fitting with a brass screen to catch dirt right at the carburetor inlet that could be part plugged. Then maybe the needle valve or float set way too low.

 

If not, a volume test at the pump. It's even possible that the fuel line is partly plugged or pinched between pump and carburetor.  

 

 

 

OK, here are links to 2 pics of the fuel pump:

https://www.dropbox.com/s/8u9m8acpr5lcuny/DSC00119.JPG?dl=0

https://www.dropbox.com/s/6pu9br0wa398afh/DSC00120.JPG?dl=0

 

It's hard to make out the brand name, but it is definitely not anything stock. You guys ever see any one like this before ?

[Charlie69]

The problem I have run into with aftermarket electirc fuel pumps on the 720 is the 720 has a return line so the factory pumps (like I pictured above) are designed to run all the time where the aftermarket electric low pressur fuel pumps are designed to build pressure and shut off.  This type aftermarket fuel pump will eventually burn it self out because it runs contiuous.  I hoard the used factory pumps when I find them in junk yards.

 

If I have to buy new I use the Facet Gold-Flo FEP60SV Electric Fuel Pump Kit Universal Petrol & Diesel Electric Fuel Cylinder Pump 12 Volt, 136 Liter/hour, 2.75 - 4 PSI

 

 

Edited April 27, 2020 by Charlie69

[Charlie69]

I have found cheaper electric pumps on ebay that look like the factory 720 electir fuel pumps but I personally have not tried them.  If you decide to try one make sure that it is a continuous duty and 2.75 - 4 PSI.  This is one from the UK and does have I believe free shipping.  I would be leery of the Chineese sellers.

 

https://www.ebay.com/itm/12V-ELECTRIC-UNIVERSAL-PETROL-DIESEL-FUEL-PUMP-FACET-RED-TOP-STYLE-CAR-VAN/233181976380

[Charlie69]

When I need a new cat I go to a muffler shop and buy the cheapest they have.  Most shops around hearhave little round ones and will install (weld) them in for about $75 dollars out the door.  These usually will last 2 to 3 years.

 

[datzenmike]

 

Mr Gasket brand. nothing special. Factory pumps last.

[sage691]

Hi guys,

 

 We tested the Mr Gasket fuel pump today and it seems to be working properly. A buddy of mine got under there and removed the hose on the output side (which was a real PITA), and then we let the pump hang down angled into a 1 gallon empty water jug cut in half. We used a timer and I turned on the ignition half way to get 12v of power to the pump. It started pumping out a nice continuous healthy looking stream of fuel and stood that way for a full 1 minute. Then when the clock showed 1 minute there was over 1/3 of a gallon of fuel in the jug. I assume this means that BOTH the fuel pump and fuel filter are OK ?

 

So I guess the next thing to check would be the fuel pump RELAY ? I found an article about this online, and I also was able to locate it on my truck. Here's a link to that article: https://axleaddict.com/auto-repair/The-Datsun-and-Nissan-Pickup-Fuel-Pump-Relay-What-the-Haynes-Automotive-Repair-Manual-Wont-Tell-You

 

So I am going to test for that next.

 

But if it is NOT that, then I am wondering could the Catalytic Converter being clogged up alone be the cause of the problem ? In other words, since I KNOW that is clogged up should I try to address that first and then see how the truck runs ?

 

And if a new Catalytic Converter doesn't fully fix it, here's my next list of things to check for:

1) pinched/clogged fuel line hose from fuel pump to carb

 2) clogged carb inlet

 3) float or needle valve set too low

 4) bad o2 sensor

 

 Now, can you guys give me any tips about WHERE that fuel line hose (from the pump) connects to the carb ? Any pics maybe of it you can post ? I am assuming I do the same thing here that I did with the pump, testing to see that over 1 liter per minute shoots out of the end of that hose ? Then, HOW do I go about testing the carb inlet with the banjo fitting ? Any tips on WHAT I am looking for there ? And the same with the float/needle valve being set too low. Any pics of WHERE those things are and WHAT they look like ? And then HOW to tell if they are set too low ? And HOW to set them higher ?

 

You guys are pretty much my life line here, and I really appreciate it ! There are NO mechanics in my area that know about these quirky Nissans/Datsuns. So the advice you guys are giving me is pure GOLD brothers !!

[Charlie69]

Here is a link to the Nissan parts manual showing the fuel lines.  The biggeer diameter is the feed to carb and the smaller line is fuel return line to the tank.

 

https://www.nissanpartsdeal.com/parts-list/1985-nissan-720_pickup/fuel_engine_control/fuel_piping.html?Filter=(1=K%2fCAB;2=Z20;3=STD;4=F5;5=LONG;6=2WD;7=CAL)

 

Ther is a "Y" pipe that the 2 rubber lines connect to and bolts to the manifold.  The bigger line is fuel to carb and the smaller line is fuel return to tank.  I will try to get a picture of the "Y" pipe fuel line in the next couple of days.  I can not find it in the parts book.

[datzenmike]

There is a way to run the pump without the relay. If the problem goes away probably the relay. If the problem persists then not the relay.

 

Test Your Fuel Pump Again

If you have not already tested your fuel pump by running a jumper wire to it, you can do it now. Build a short jumper wire and connect the blue terminal to the white/black terminal. When you turn the ignition over to the accessory position, you should now hear the fuel pump running constantly (not recommended as a permanent fix)!

 

[sage691]

3 hours ago, datzenmike said:

There is a way to run the pump without the relay. If the problem goes away probably the relay. If the problem persists then not the relay.

 

Test Your Fuel Pump Again

If you have not already tested your fuel pump by running a jumper wire to it, you can do it now. Build a short jumper wire and connect the blue terminal to the white/black terminal. When you turn the ignition over to the accessory position, you should now hear the fuel pump running constantly (not recommended as a permanent fix)!

 

 OK, so you're implying that there still might be a problem with the fuel pump even though it passed the first test (output volume) ? Like maybe once the engine is running it starts to output less and starve the carb ? I am just a bit confused, so sorry if I sound ignorant -- which essentially I am when it comes to car mechanics (lol)😄.

 

 I am not sure what that relay actually does, but I thought it might somehow control the flow of fuel to the carb POST the fuel pump output line. Is that correct ? And so, if the relay is malfunctioning then even though the pump is good the carb will still be starved of fuel ? And the "jumper wire" test will reveal something different than the other test I did ? 😟

 

 

Edited April 28, 2020 by sage691

[datzenmike]

No, I'm implying that the fuel pump relay might be a problem. If the relay is faulty it might shut the pump off and it would act like it was running out of gas. A jumper wire from Blue to White/Black (stripe) causes the pump to be on regardless of the relay. If the problem goes away it's the relay, if problem stays then it's not the relay.

 

I know this is a slow process but if you were to run out and buy a new electric pump that wouldn't have fixed the problem, nor would a filter.       

[sage691]

4 hours ago, datzenmike said:

No, I'm implying that the fuel pump relay might be a problem. If the relay is faulty it might shut the pump off and it would act like it was running out of gas. A jumper wire from Blue to White/Black (stripe) causes the pump to be on regardless of the relay. If the problem goes away it's the relay, if problem stays then it's not the relay.

 

I know this is a slow process but if you were to run out and buy a new electric pump that wouldn't have fixed the problem, nor would a filter.       

OK I get it !

 

So just to be clear, I first remove the screws attaching the relay so I can access those wires in that plastic connector more easily. I leave the plastic white harness connected to the black relay box. Then I take a small copper wire (16 or 18 gauge) and stick one end in the hole for the Blue terminal, and the other in the White/Black terminal. Then start up the truck and take her for a long spin and see if she is suddenly starts running consistently better. And if she does, then I know the RELAY is the problem.

 

Sounds not too hard, and hope I didn't get anything wrong. I'll do that and report back.

 

BTW, yes it is a long process but I am actually enjoying the challenge !

Edited April 28, 2020 by sage691

[bilzbobaggins]

On 4/28/2020 at 2:11 PM, sage691 said:

OK I get it !

 

So just to be clear, I first remove the screws attaching the relay so I can access those wires in that plastic connector more easily. I leave the plastic white harness connected to the black relay box. Then I take a small copper wire (16 or 18 gauge) and stick one end in the hole for the Blue terminal, and the other in the White/Black terminal. Then start up the truck and take her for a long spin and see if she is suddenly starts running consistently better. And if she does, then I know the RELAY is the problem.

 

Sounds not too hard, and hope I didn't get anything wrong. I'll do that and report back.

 

BTW, yes it is a long process but I am actually enjoying the challenge !

 

 

And whats the verdict?

[datzenmike]

You can leave the relay unplugged and just use the jumper wire.

[banzai510(hainz)]

Water under distributor cap

get a hair dryer

Edited May 3, 2020 by banzai510(hainz)

[sage691]

Hi folks,

 

OK, time to report back my results with the "relay". This may be a long winded post as I want to be as thorough as possible with all the details.

 

So on Thursday I had a friend remove the relay black box. It was a PITA to remove and he had to use a rachet with a phillips screw head inside as those 35 year old screws feel like they are welded shut ! But he got it off and we took a look at it, and LO AND BEHOLD there was immediate evidence of moisture/water damage !! I took 2 photos to show you guys and here are the Dropbox links:
https://www.dropbox.com/s/vmp6ixvyljahv9t/DSC00117.JPG?dl=0
https://www.dropbox.com/s/y8cya29j1qcg9o1/DSC00120b.JPG?dl=0

 

The first photo shows what appears to be some type of paper cover that sits over the circuit board, I guess to protect it from moisture ? You can see how it seemed to shrink back and also that greenish mildew from water/moisture. Then the 2nd photo shows a line of black bubbly goo that looks to be evidence of some component overheating on the other side of the circuit board. This is definitely NOT solder flux either. My guess is that on the other side there is a burnt out resistor, capacitor, or diode.

 

And now I feel a little stupid. Why ? Because when I first posted I forgot to mention the LEAK that just so happens to be right over where this relay switch is located. Yep, when it rains hard I have been seeing some water on the carpet by the passenger seat. And when I traced it a few days ago (after a HARD rain) I saw evidence that water is getting in by the bottom corner of the front windshield. I had no idea that crucial electronic components would be placed in such a precarious position, so I figured the leak was no big deal.

 

So I took "Datzenmike"s advice and made up a little jumper wire from two 24 gauge phone cable wires twisted together, and I stuck each end in where the diagram showed. Remember that I had already tested the fuel pump and it was pissing out fuel like a drunken sailor.

 

Here is what I noticed in chronological order:
1) When I turned the key to the pre-start position I immediately noticed a sound (by the carb) that I hadn't heard in a LONG time ! This is a rapid fire "clicking" sound (32 or 64 per second), like the speed of a machine gun. The fuel pump makes a buzzing type sound, and that was the only sound I had been hearing since the truck started really acting up. Heck, it's been so long I had forgotten about this sound. But the moment I heard it I remembered it, and when the truck ran good that sound was always there.
2) The truck started up easily and immediately had a nice smooth idle. Before I would have to keep my foot on the gas for at least 1 minute, revving the engine pretty high just to get it where it wouldn't sputter and kill out. It had been a LONG time since the truck started up and idled this easy from a cold start !
3) I was able to rev the engine VERY high without it sputtering, making fire cracker sounds, etc. It felt a lot smoother for sure, and then when releasing the gas it came back down to a smooth sputter-free idle.
4) So I took her for a ride and WOW -- she hadn't run this smoothly in a long, long time ! So long in fact that I realize this must have been a problem going on for years now. That day I drove her around De Saix Ave. (a close street with a straight run for about 1.5 miles in each direction) for about 30 minutes. Every time I got to the end of the street I would turn around and start from 0mph and get her up to 50mph until the next turn around. I must have done that 15 times before pulling back in to the garage. I was in disbelief that a defective little relay switch could reek so much havoc on the performance of a vehicle, rendering it almost dead ! I let her sit for another 10 minutes and we adjusted the idle on the carb down as it was WAY too high ! Then I took her out on the highway and got her up to 60mph with no problems. The truck was on for over 1 hour all in all, and NOT ONCE did it have anything close to the symptoms it had before !
5) Another thing I noticed is that the largest fuel hose attached to the carb was significanty less hot than it was before ! I mean, this hose was so HOT before that if you tried to squeeze your fingers around it you would have to remove them in 1 second or you would get burned badly. But now, after running for over 1 hour it is just very warm and I could grab it and hold it for as long as I want and not get burned. I am not sure what this hose is so I took a photo of it for you guys. In Photoshop I made a red line in the middle of it.

 Here is the Dropbox link to that: https://www.dropbox.com/s/5l0r5dzkxjclzml/DSC00122.JPG?dl=0

 

 I have been running the truck now for several days and it hasn't missed a beat ! It runs better now then it has in years, and also the temp gauge stays lower and never even makes it to halfway before the thermostat opens up -- before the temp needle would go to the halfway mark, then back down a bit once the therm kicked in. So I assume the engine is running cooler as well which was a surprise; I didn't know that a fuel starved carb would cause an engine to run hotter. I am still convinced that the catalytic converter is clogged and needs replacement, but it was definitely not causing the the engine to lock down like it was.

 

So my "to do" list now is:
1) Order a new Relay, or possibly even try to fix the old one myself. It looks as though I can de-solder those pins and access the guts on the other side. If a diode, cap, resistor burned out I can probably get a replacement for pennies. And it's GOOD to know I can remove the relay completely and still run the truck -- so thanks "Datzenmike" for that tip !! I won't leave it like that for more than a week or two at the most.
2) FIX THE LEAK ! I guess I will need to look on Ebay for the full weatherstripping set that seals the front windshield, and maybe the two front doors as well. Any tips on WHAT to buy and WHERE to look for that stuff guys ?
3) Replace the Catalytic Converter. We looked at it closer, and it does appear to be the removable kind -- it has old rusted out bolts and nuts at the inlet and outlet sides. I bought some deep penetrating lube for those, so my buddy said he would like to give it a go. I saw new ones on Ebay for $40 so the cost is no big deal.
4) Re-attach the fuel pump. Right now it is "rigged" in place with wire as the bolt broke off inside the threaded hole upon removal. We are going to have to think outside the box to try and get that re-attached securely.
5) Buy a new gas cap. The old one is in pretty shabby shape and is likely letting moisture into the gas tank.
6) Probably get new hoses from the gas tank to the fuel filter, filter to pump, and pump to carb. Those hoses look as old as the hills to me !

 

 Well, that's about it for now folks. I am so, so grateful to "datzenmike" and "Charlie69" for all of the help you guys provided. It would have been IMPOSSIBLE to figure this out without your help, and I am deeply appreciative. If you have any tips on my "to do" list above I would appreciate that as well. This baby only has 285,000 miles and so I am hoping she is good for another 500k at least !

 

Edited May 4, 2020 by sage691

[captain720]

I had a windshield leak that took out my whole fuse block and burned up my heater motor (it was a smoky event)  I would just have a glass shop do it. We have one here that will do a windshield for what I can get glass and a gasket for. Just my 2 cents, like you I wish I had done it years earlier. But money and priorities you know how it is.

 

Now you get to retorque head bolts and stuff. I have a "basic maintenance" playlist on You Tube that should help you get to 500k.

Edited May 5, 2020 by captain720