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Another EFI problem


EdMo

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Somewhat similar to the one posted a few days ago, I still can not find my problem. I have a 1978 280z w/EFI and have replaced pretty much everything in the fuel flow, except for the Pressure regulator and Dampener. It starts no problem, runs for 15-20 minutes no problem, then starts to putter and enventually stalls at idle. It's then difficult to start unless you let it sit for 20 minutes or so, then starts easy and the same scenario all over again. I'm thinking it's the fuel pressure regulator .... does anyone have opinions on this?

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After the car has sputtered and died, pull off the vacuum hose from the fuel pressure regulator. It should be dry, but if the FPR has developed a leak, it most likely will have gas in it.

Another possibility is that your fuel pickup screen is getting clogged up. That would make sense considering it takes about 20 minutes to do this, whereas a bad FPR would be a non stop sort of thing (lack of power, fuel in oil).

FWIW

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Got ya, I'll check the vaccum hose on the FPR tonight. As for the fuel pickup screen, not sure what you are referring to or where, I've put in a new filter, pump, all fuel injectors and sensors are new as well. Thanks for your response. Now I did not replace the connectors that go to the new fuel injector temp sensors and cold start temp sensor....thinking of ordering.

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That sounds like a fuel filter clogging up to me. I know you say that you replaced it, BUT after I read "I am the original owner of my 1978 280z, though set it to rest in 1996 and started restoring it last year in March of 2007. It's been fun and still on going..." This tells me that it sat for 11 yrs. so what more than likely happened is during its "rest" that gas in the tank got very old and crappy, plus possibly a little rust inside the tank with moisture so even though you replace the filter and clean the lines, this "crud" in the tank is breaking loose and constantly clogging stuff up and creating this issue your having. It just makes all too much sence. Then once you have the car off for X number of minutes, she is fine again because the junk has settled, but once the flow stirrs stuff up again when the car is running, then it starts blocking the flow up again which results in poor idling, or killing the motor.

Sounds like a new fuel tank is in order, or have it professionally cleaned internally. Just simply draining out the old fuel doesn't cut it.

As for that additional fuel filter, it's a small one located at the inlet side of the fuel pump. For sure replace that as well. Hopefully the crap hasn't clogged the injectors :ermm:

Anyway those are my thoughts.

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DatsunZs Rule...your absolutely right. What I meant about it sitting 11 years, it did untouched. I did not start restoring it until this last year March before breaking it all down, I did get the tank professionally cleaned with new pump and had a problem starting until I replaced the FI sensors and got it started. It was amazing that it ran pretty good, but I new I wanted to do a restore and rebuild, we just wanted to make sure we could get it to run before the tear down. Since, I had the motor rebuilt all new fuel injectors and sensors and a whole lot more to list all. I do need to check this small inline filter, is it closer to the tank or filter? Thanks.

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Have you tested the cold start, thermotime, and water temp sensor? Maybe one is telling the efi that it is cold and thus too much fuel is being injected once the car warms up? Do something to trick the system into forcing the sensors to read hot. I don't have my fsm as I am traveling and I forget whether the sensors are on or off when cold/hot.

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I probably will not be able to check the inline filter until Saturday .... but I will....oh I did check the Fuel Reg. after it bogged at the vaccum hose and it was dry (suggested in a previous post-thx). As for the sensors, I did replace the FI temp sensor and water temp sensor, I did not see in Blackdragon or Motorsport catalogue of a cold start sensor available or mentioned to order.... so I did not replace it, thinking it starts fine at cold, though it does make sense of getting to much gas after warm up. Also the connectors that wire up to them are old and tried to clean but still not sure if making good contact. Do you know whether the cold start sensor is the same as the FI temp sensor and where I might be able to find the mating connectors? Also, after warm up you can here the fuel pump humming (this is the second pump acting the same) and can smell gas, so it almost seems like its choking itself.

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Have you tested the cold start, thermotime, and water temp sensor? Maybe one is telling the efi that it is cold and thus too much fuel is being injected once the car warms up? Do something to trick the system into forcing the sensors to read hot. I don't have my fsm as I am traveling and I forget whether the sensors are on or off when cold/hot.
Sounds to me like you need to read the FSM a little more to understand the function of the components you mention. They don't 'tell' the system anything. They're much simpler than that as it the system. No need to 'trick' the system into doing anything. Even if you accomplished that, what have you really accomplished? A problem would still exist. Check each of the mentioned components as per the FSM. There is a test procedure for each one as well as the rest of the components in Section EF.
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Okay so the word "tell" is not quite right. The Thermotime and temp sensor do react to temperature and based on their reaction the brain does something.

And, the cold start valve could be malfunctioning and injecting fuel when it should not.

And yes, I have read the fsm but I will note your advice.

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The temp sensor is a thermister which decreases in resistance as the water temperature rises. The lower the resistance the richer the fuel mixture and vice versa. The thermotime switch is a bimetal contact that reacts to water temperature and a heater that reacts to electrical current that comes from the start signal. It sends a signal to the cold start valve while cranking when the water temp is below 72 deg. F but only for a maximum duration of 9 seconds due to the heater to prevent flooding. The cold start valve, which is basically an injector, can malfunction like a leaking fuel injector or dispense fuel because of a malfunctioning thermotime switch. The 'brain' as you call it doesn't do anything except patch signals through from one area of the system to another based on the signals it receives, or doesn't receive from the components of the system, generating a fuel injection pulse. It's not a brain, as such, compared to the modern fuel injection systems in that it makes no adjustments, calculations, etc. It's just three integrated circuits on a board in a box.

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So far everyone has you looking at fuel. maybe it's on the spark side. i've seen Nissan distributers cut out when they get hot (roughly 15-20 minutes after start up0 die, then run again after they cool off. Try this, get an extra spark plug, new or used, and next time the car dies pull a plug wire, plug it to the extra plug and ground it by the strut bolts. Try cranking the car and see if you are getting spark. At worst this will eliminate the dizzy as the culprit. Speaking of plugs, have you checked them to see if the car is running rich when it dies? To much fuel will kill the car, but it will usually smoke black smoke first.

Jim

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Yes, I have also checked the plugs as well, only a month old they did seem a little more carbonized as running rich. Now the engine itself has only about 600 miles and the rings should have already set, but these are the same plugs during the breakin. So I went ahead and replaced them with some plugs that I had previously used during the first start up. The problem remained the same.

Do want to say quickly thanks for everyones input .... I've got alot to check, unfortunately most is on weekends because of work.

I did speak with Mike Mcginnis from Bonzai Motorworks this afternoon, mainly because I was ordering the subharness connectors for the sensors. I have replaced the Thermo sensor, sending unit sensor but did not replace the cold start because I did not see it in catalogue when ordering other sensors. So I am also getting the cold start sensor as well, but probably will not get here till next week. Mike also had alot of information, some as other posts earlier, but he highly suggested I do this as well. He also recommended to change the Fuel Pressure Regulator everytime you change the fuel pump. Its the original regulator so I'm sure it would be a good idea to replace as well. I've got to much $$ invested to quabble over a few more bucks.

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Fine Stephen...whatever techicalities you like...I suggest that the original poster focuses on these three components. It is my suggestion based on my experience with the car and I stand by it.

Not to start an argument here, but Stephen's response to how those E.F.I. components work on a stock 280Z IS correct wheather you want to believe it or not :classic:

Anyway back to the original posters questions-

"Do you know whether the cold start sensor is the same as the FI temp sensor and where I might be able to find the mating connectors?"

No such thing as a Cold Start Sensor or F.I. temp sensor. I'll try to clear things up here for you. There are only 2 main temperature sensors in the 280Z Bosch L Jetronic system. One for coolant temp. and the other is for air temp. The Water Temp. Sensor is located at the Tstat housing and the air temp sensor is located in the A.F.M. (Air Flow Meter)

Stephen has already explained how these function in his post above so no need for me to repeat it.

As for the connectors- are you looking for a injector connector for the Cold Start Valve? If so, Courtesy Nissan has them www.courtesyparts.com

"Also, after warm up you can here the fuel pump humming (this is the second pump acting the same) and can smell gas, so it almost seems like its choking itself."

If your smelling gas then check for leaks. perform a fuel pressure test if you have the equipment to do so. If not then at the very least do a visual check. For the pump, does this noise happen with a full tank? Reason I ask is because they will make more noise when the fuel in the tank gets lower. Also what brand of fuel pump did you install? Aftermarket or Factory?

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The sensors I was referring to, are located at the thermostat housing, which Mike mentioned were the Thermo Time Sensor and the Wather temp sending unit and the other that I had not replaced was the water temp sensor. At the Z Clinic here in Austin, these bullett connectors and sensor were there main concern and they explained as cold start sensor and FI temp sensors. Though he did mention they adjusted the AFM, but not sure what adjustments were made. But before and after this the problem is the same, so anything they did...did not help or make a difference. I have checked for fuel leaks all around, but do not see any.

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You know, I really don't see it being a sensor. The only one really effected by time/ temperature is the head temp. We need to know what's going on when it dies. Try the spark plug test for spark. see if you can get a noid light ( I believe that advance auto sells them for about $12) and test for injectors firing. A fuel pressure gauge will help make sure the pump,regulator and filters are all OK. Those three tests will really help to narrow down the possible causes. I'll still guess it's spark, but that's just a guess. To bad you weren't closer to Tampa, I have both types of factory EFI analyzers.

Jim

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Hot dang it...call me stupid, but what I have replaced is the water temp sensor, the water temp sending unit and have not replaced the Thermotime sensor or the Cold start valve.

I wish I were closer to Tampa.

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I too have all the equipment but I'm in MN. My Z is still in winter storage :( So I'm unable to lend a hand as well since your in Texas but anyway, I hope you aren't just replacing things because you think they are bad or the cause of the problem. You'll take yourself to the poor house doing that.

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Did you check the programming on the engine computer? Sometimes it'll get oout of balance and you need to go inside an press the reset button to get it back to the default settings, so it doesn't shut off the fuel pump when the coolant gets too hot.

Well, you can't do any of that :cheeky:, because the ECU ( Engine Control Unit) is about as dumb as a transistor radio. It just takes inputs from the coolant temp sensor, the air temp sensor, AFM resistor, etc. and generates pulses to turn the injectors on. It's not anything like a computer or a brain, and if you ever get any work on it by a 'modern-trained' mechanic, you'll know better if he tells you that you need a new engine computer, or you can reprogram ( 'rechip') the engine computer for performance.

Remember the L28 engine is of the old-school design, which relies more on the mechanicals to get power. the ECU is there to make sure it gets the fuel it needs for the temperature, RPM, and airflow.

You would do well to get yourself a copy of the '280Z EFI bible.' It has diagnosis charts and procedures. Also atlanticz.ca has several tech sections which describe how you can test sensors and other stuff.

thxZ

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One of the main problems with these systems is the lack of understanding of them. And it gets spread around enough to where people end up throwing parts at a problem until it's fixed. I prefer not to take that route. jonathanrussell, you can respond to what I say with a surly attitude; that's your call. My cars run. I don't come here for advice as I've worked on these cars for over 30 years. I'm not trying to prove anything. I would just like to see correct information. You do it your way, I'll do it mine. I would also like to see him get his problem corrected without seeing terms like 'brain' or 'tricking' the system. Call what I said 'techicalities' if you wish but that's how the system works.

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Not to start an argument here, but Stephen's response to how those E.F.I. components work on a stock 280Z IS correct wheather you want to believe it or not :classic:

I don't recall questioning Stephen's response or indicating that I don't believe it. I am though tired of him picking at my terminology when i am merely trying to point the poster in a direction that seems to make sense to me. Car runs good when cold. Car warms up and immediately falls apart. In my experience...and I have experienced something similar...it is the thermotime sensor, water temp sensor, or cold start VALVE.

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You will note by my statement which was

Check each of the mentioned components as per the FSM. There is a test procedure for each one as well as the rest of the components in Section EF
that you and I are on the same page. I just think it's important to use the correct terminology especially when responding to someone who, at least by the content of his post is not as experienced with the system and it's troubleshooting as you or I or many others on this site. I won't say anything else along those lines here since it seems to bother you so much.
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I just think it's important to use the correct terminology especially when responding to someone who, at least by the content of his post is not as experienced with the system and it's troubleshooting as you or I or many others on this site. I won't say anything else along those lines here since it seems to bother you so much.

Fair enough. I will try to use the right terminology in the future if I am going to give my suggestions.

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