MJ Comanche Tech. Stock & Modified. MJ (86-92)
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88 Renix fuel issue......please help

Old 05-01-2017, 11:09 AM
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Default 88 Renix fuel issue......please help

Hey everyone, I just acquired an 88 MJ with just over 200k, auto and the infamous Renix 4.0. When we got the truck it wasn't running but it was cheap...🙃

The problem seems to be no fuel is getting past the regulator....fast forward to new pump, filter, some new fuel line, and regulator but fuel still won't get past the regulator.

Someone told me to pinch the return line shut and try to start it, amazingly the truck fires right up when we did that but when I remove the line locks from the return line it does 30 seconds later.....

Any ideas to try next would be greatly appreciated....thanks!!!
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Old 05-01-2017, 07:53 PM
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Test your fuel pressure with a gauge to verify you have 31 at idle and 39 with the vacuum hose pulled from the regulator
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Old 05-01-2017, 07:58 PM
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It's zero pressure unless I'm crimping the return line. I haven't felt the need to test pressure while the line is crimped and it runs so poor..... there's something I need to find/fix before I get into fuel pressures being correct you know.
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Old 05-01-2017, 08:15 PM
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Well then, perhaps the fuel pressure regulator isn't holding pressure in the fuel rail or the fuel pump is weak.

With a fuel pressure gauge on the fitting, the fuel pressure should shoot up to about 100 PSI when the return line is crimped if the fuel pump is good.

That should help narrow it down.
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Old 05-01-2017, 08:39 PM
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I've replaced the regulator 3 times and the pump twice.....i mean it could be possible I've got bunk one's over and over but I feel it's highly unlikely
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Old 05-01-2017, 08:44 PM
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Originally Posted by classicgranola View Post
I've replaced the regulator 3 times and the pump twice.....i mean it could be possible I've got bunk one's over and over but I feel it's highly unlikely
Well, one of them makes pressure and the other one controls pressure.

One of them isn't working.

If you got an Airtex pump, it's possible you got a few bad ones.

How much voltage do you have at the pump while cranking?
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Old 05-01-2017, 08:52 PM
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I'll have to check the voltage, what should it be?
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Old 05-01-2017, 08:57 PM
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About 12 volts DC.
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Old 05-01-2017, 09:00 PM
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Awesome, I didn't try that yet but I'll give it a shot, thanks!!!
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