Hard start when hot

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Aug 15, 2018
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Tulsa, OK
Hey all - Having a little issue with my 97, now that it's finally running after 4 years. The engine has been running really well (from what I can tell), but I'm having a bit of an issue that seems to correlate to when it's either really hot outside or if the engine is hot. When cold, the engine starts right up, but when hot, it takes quite a few cranks to start - and it sounds like it's a fuel starvation issue? In reading through the other posts on this issue, most were resolved by replacing the Fuel Pressure Regulator. Based on that, I changed mine as well but there's been no noticeable change.

When it's having this issue, it cranks for a bit, then sputters, then finally starts normally. I'm assuming the next step would be a fuel pressure test, but I've never done that before, so I would have to get a test kit and check the FSM... Just unsure what to look for with that or what that would tell me yet (need to read the manual). Am I on the right path or are other things to check? Since it'd been sitting for at least 4 years, I wasn't sure if the injectors could be an issue or if the charcoal canister could affect this (both are original). I am getting pressure blow off when I take off the gas cap to fill up, so that's also on my list of things I need to remedy.

Other engine maintenance completed (I may have forgotten to list some as it's been awhile):
  • OEM distributor housing, rotor, cap
  • OEM plugs, wires, coil, seals, valve cover gasket, oil pump gasket, front main
  • OEM rad, hoses, water pump, thermostat, fan clutch, fan
  • OEM alt rebuild
  • OEM fuel filter
I don't have any CEL if that is helpful. Thanks for any ideas :) I'll try to capture a video of it today.
 
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COYS

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There is another recent thread that chased after something similar. IIRC, it was resolved by replacing the fuel pump.
 
Joined
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Tulsa, OK
There is another recent thread that chased after something similar. IIRC, it was resolved by replacing the fuel pump.
You're right - in my searches I did come across that as well. I'm pretty sure the fuel pump has been replaced recently, but I'll double-check that too... Thanks!
 
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I'm assuming the next step would be a fuel pressure test, but I've never done that before, so I would have to get a test kit and check the FSM... Just unsure what to look for with that or what that would tell me yet

I did this. It's a pain because you have to remove a banjo bolt at the back of the fuel rail. The engine wiring harness is in the way, making it a bit stressful when you're trying not to cross-thread the adapter. What it will tell you is whether or not the fuel rail is receiving the pressure it needs to operate correctly (70psi? I don't remember).

If it's low, it could be the fuel pump, a clogged fuel filter, or a bad fuel pressure regulator. I guess it could technically be a clog anywhere in the fuel lines, but I've never heard of that happening.

You might as well take a look at the fuel pump. Make sure it's Denso. Aftermarket fuel pumps can really be total garbage.

When you're having the hard-start issue, you might want to unscrew your gas cap and see if there's a vacuum. IIRC, the gas cap has a one-way vent to allow air to enter the tank, and it can become clogged. I've definitely heard of vehicles that become starved for fuel under such conditions.
 
Joined
Aug 15, 2018
Messages
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Location
Tulsa, OK
I did this. It's a pain because you have to remove a banjo bolt at the back of the fuel rail. The engine wiring harness is in the way, making it a bit stressful when you're trying not to cross-thread the adapter. What it will tell you is whether or not the fuel rail is receiving the pressure it needs to operate correctly (70psi? I don't remember).

If it's low, it could be the fuel pump, a clogged fuel filter, or a bad fuel pressure regulator. I guess it could technically be a clog anywhere in the fuel lines, but I've never heard of that happening.

You might as well take a look at the fuel pump. Make sure it's Denso. Aftermarket fuel pumps can really be total garbage.

When you're having the hard-start issue, you might want to unscrew your gas cap and see if there's a vacuum. IIRC, the gas cap has a one-way vent to allow air to enter the tank, and it can become clogged. I've definitely heard of vehicles that become starved for fuel under such conditions.
Thank you - What did you find out about yours when you did it? It help you pinpoint your issue?

The shop that replaced my rusty fuel tank and lines also replaced the fuel pump (I'm 95% sure), but it was probably a used assembly. I'm going to stop by that shop today so they can check a few other things and will let them know. I was hoping the new fuel pressure regulator would've solved this problem, but it didn't.

I'll be sure to circle back here on what the resolution is, once I find out :)
 
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Could also be a temp sensor, as the fuel pressure changes by fuel pump voltage when it is up to temp and moves into closed loop operation. There are two temp sending units on the engine. One for the gauge and one for the ECU.

Also has been known to be the VSV.
 

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