need help car starts but will turn off after a few secs

[jesus]

7 hours ago, Zed Head said:

I'm guessing that you were pointing out that he said "fuel was flowing pretty good"?  Hard to tell when he saw the fuel flowing.

Everything could be set up perfectly but if he has one of the big hoses removed, like the PCV hose, it will start and die like he's describing.  Might just be a giant vacuum leak.

i have that same feeling a leak somewhere or injectors in a way i have all my hoses connected i will see if i find any cracks anywhere 

[EuroDat]

Hi Jesus,

We have been PMing over your HEI module swap and I missed this thread altogether.

Your problem could be caused by a number of issues or even a combination.

The AFM switch is a common cause. The AFM has a cap with silicone kit. You can gently cut the kit and remove the cap to check the switch. Check the switch adjustment by reaching in from the air filter side and moving the vane or turning it by the counter weight by hand.

Check for vacuum leaks. There was a thread on here called the Yoghurt cup test, but I can find it anymore. Basically its just removing the hose between the AFM and the throttle body and blocking the hole with a yoghurt cup. The removing a hose so you can blow air into the manifold with your mouth and searching for leaks with soapy water.

Fuel pressure and pump capacity are also things that can cause your problem. Buy a simple gauge and you can do some symple test to check the pressure and flow. A blocked filter can be so bad, that the car will idle, but the pressure will drop right off when you open the throttle and need more fuel.

The fuel system has infact two filters, one in the pump inlet and the filter at front right side of the engine. See the instruction in the pdf. It is for checking leak down, but the flow test and basic pressure check while running engine is what you need.

Check the earth terminal on the top of the inlet manifold. It is very important for the EFI. And check where it connects to the body on the side of the strut tower.

Cheers

Instruction - Fuel Pressure Test 280Z RevA.pdf

Edited January 19, 2018 by EuroDat

[siteunseen]

Hard to find the original thread like Eurodat says.  Here's the best I could do with my phone.  Hope you find something useful.

http://www.classiczcars.com/forums/topic/49816-help-with-yogurt-cup-test-please/

[EuroDat]

Godd work Siteunsen. I couldn't even find that one. I did find one where someone was asking about the yogut cup test.

It might have something to do with the migrating from the old server to the new one.

[siteunseen]

I googled "fastwoman yogurt cup test classiczcars.com"

Works every time. 

[jesus]

the weird thing is that i dont have non of those grounds on my car the two that it shows on the picture and i will see what is happening to my afm 

[EuroDat]

Jesus, When you check the earth wiring, check at the battery as well. The photo I posted is from a 5/77 model. Somewhere in 76 they changed from earthing the body to the battery to the style in the photo. Not sure which month they did it. 

Yours might be ok, just located at the battery. If that is the case, check the negative battery post for three cables, the large heavy duty cable for the starter, another cable with a connector (ECU ground) going over the firewall towards the brake booster and one going to the body just behind the battery.

I made a couple of screenshots to show the difference. 

Chers

 

[jesus]

Ok guys so I can get my car running for a few seconds whit out any throttle then die out I got it to do it by disconnecting my afm dose that mean I need a new one ? It looks pretty clean in side it idk what else can be i also cranked it when cover was off and it looks like it just flickers back and forth fast can it be that some else going to the afm is bad ? 

[Zed Head]

Did you disconnect the AFM hose or the wires?

Spend more time composing your post before you send it.  Describing the problem will help you understand it too.

[EuroDat]

Yes, What do you mean by diconecting the AFM?

If you mean disconecting the 7-Pin plug, then yes it will start, but it will never run more than a couple seconds because the fuel switch is in the AFM.

The fuel pump is activated by the key contact when it is in start position and after that it is operated by the contacts in the afm.

What was it doing before you disconectdd it. Would not fire at all or ??

Interesting adjustment method on the 76 model. It uses a screw on the counter weight like the 78 where the 77 has a tab in the housing. Not helping you any, but just interesting to note the small changes.

[tzagi1]

Inspect for a cracked boot between the afm and the tb, black silicone works wonders.

[jesus]

yes disconnecting the plug on the bottom and it will start but before doing so it will stay cranking and it will not start my car it is a 75 but not sure what year the engine came out of sense last owner did a poor job on the swap the reason why im having this problem its because last owner left the transistor sys on the ground and it sparked and i dont know what it could of killed it was running and driving when i got it so what i did is changed the ign sys whit a gm part instead of the transistor i know my relay that controls my injectors works so i dont know what else it can be