no fuel pressure at startup

[mko1976]

1996 5.7L will turnover but won't catch without spraying starting fluid into intake while engine is cranking. Fuel pressure test listed psi at 52, which dealer said was adequate. Several mechanics recommended replacing fuel pump, pulsator and/or regulator. Did all the replacements myself and still no start. Can't quite figure this one out.

[mko1976]

Forgot to mention that once started, the engine runs just fine. There's no loss of power at all, which tells me it's something other than a simple fuel pump issue.

[bartlanz]

Have you check that you are getting GOOD spark?

[gurrzt]

If you had "no fuel pressure at startup" the vehicle would not start up at all.

[Jeremy-WI]

Might want to change the fuel pump relay. If the pressure is 52 psi at idle it may be OK. It should be 60-66 psi with key on engine off

[blakey2000]

did you ever figure this out? I have the exact same problem! help!

[email protected]

[dmueller]

Originally Posted by blakey2000

did you ever figure this out? I have the exact same problem! help!

[email protected]

I also have the same problem, with no help at this time, I've tried Fuel Filter replacement, Fuel regulator replacement, fuel pressure checks, heard possible cause might be fuel pump pulsator???

Did you get your problem resolved? If so, what was the culprit??

[email protected]

[Rs051802]

Have you checked your fuel lines. You could have a collapsed line. Check the pump relay, check your injectors for a strong spray. Does your pump turn on when the key is turned forward? You should be able to hear the pump come on. Oh yeah, I am sure you will not like this, but very often replacement pumps are bad from the get go.

[MT-2500]

Ok here is a starting point for everone.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

MT

[dmueller]

Here is a little more history, about my engine start problem (starving for fuel). My basic symptoms are pretty much identical to what "MKO1976" had on the previous post from 06/94. My initial pump psi jumps up to approx. 52psi when applying initial power to the pump (key on position - prior to actual cranking). Then there is an inconsistant boost in pressure, that sometimes raises the pressure to the low 60's range from the initial 52psi uaually seen at initial key-on. This occurance is noticed when slowly moving the key from the "on" position to the crank position, where as sometimes (but not always) the pump re-cycles for a couple more seconds (if turning the key slowly between the "on" and "crank" position and this booosts the pressure to the low 60's range, but this is without ever having lost any of the initial pressure of 52psi obtained on initial power application or keying to the "on" position, prior to cranking. When I checked the bleed-back, it read approx 7psi decrease within 5 minutes, which is slightly more than the "5psi within 5 minutes" that the spec's I found say. I didn't think this bleed-down to be too big of an issue, since re-keying prior to attempting to start, boosts the psi right back to the initial 52psi area, if not up to the occasional low 60's. I haven't seriously worried about the F.P. relay, since the pump always goes through the approx. 2 second cycle of bringing the pressure up to at least 52psi just on initial key power, prior to the 2nd pump cycle that I see occasionally while moving the key from "on" to the "crank" position, which once again does sometimes boost the pressure upward to slightly over 60psi or low 60's before the cranking actually starts.

Once again with the same senario as "MKO1976", manually priming via the air intake, will get the vehicle to start, pretty much withou fail, at least it has up until this point in time. Once started there is aboslutely no indication of fuel starvation what-so-ever and the pump (at an idle) keeps the pressure in the low 60's range. Lightly reving the engine, causes the pressure to jump higher into the mid to upper 60's momentarily while performing the reving. I have not yet performed a fuel pressure reading while driving on the road or with the return line pinched off.

Recently I've read and heard that there is a fuel pulsator, that may cause this problem, particularily if cracked (apparently inside the fuel tank, above the pump). Apparently the original equipment pulsator, can crack from fuel with too high of an ethanol mixture, and newer replacements are built to handle the higher levels. The maximum mixture I believe sold at normal gas pumps (not E-85) is a 15% mixture, which I'm sure I have had enough of, but I haven't ever put higher mix levels in, unless the wrong gas was in the regular fuel tanks at any given station. I suppose that is quite possible, but maybe unlikely...

The vehicle runs so very good (normal) once started, that I have no problems at all driving full highway speeds, even when towing my double axle 16' enclosed trailer down the road. Other than potential bleed back issues (like a weak or leaking check-valve or pulsator) it makes me wonder how the pump could perform so good once running, yet not perform up to par only at start-ups. I'm baffled with this one! Any further help or suggestions would be greatly appreciated! I was hoping someone has had the exact same problem as it seems that "MKO1976" and I have experienced and tell us what was done to resolve the issue, hopefully short of the entire fuel pump module replacement. I've also read that pump module replacement without the fuel pulsator replacement can lead to a repeat scenario? Actually I though a pump "Module" would incorporate the pulsator, though in reality it may not.

dmueller

[MT-2500]

Originally Posted by dmueller

Here is a little more history, about my engine start problem (starving for fuel). My basic symptoms are pretty much identical to what "MKO1976" had on the previous post from 06/94. My initial pump psi jumps up to approx. 52psi when applying initial power to the pump (key on position - prior to actual cranking). Then there is an inconsistant boost in pressure, that sometimes raises the pressure to the low 60's range from the initial 52psi uaually seen at initial key-on. This occurance is noticed when slowly moving the key from the "on" position to the crank position, where as sometimes (but not always) the pump re-cycles for a couple more seconds (if turning the key slowly between the "on" and "crank" position and this booosts the pressure to the low 60's range, but this is without ever having lost any of the initial pressure of 52psi obtained on initial power application or keying to the "on" position, prior to cranking. When I checked the bleed-back, it read approx 7psi decrease within 5 minutes, which is slightly more than the "5psi within 5 minutes" that the spec's I found say. I didn't think this bleed-down to be too big of an issue, since re-keying prior to attempting to start, boosts the psi right back to the initial 52psi area, if not up to the occasional low 60's. I haven't seriously worried about the F.P. relay, since the pump always goes through the approx. 2 second cycle of bringing the pressure up to at least 52psi just on initial key power, prior to the 2nd pump cycle that I see occasionally while moving the key from "on" to the "crank" position, which once again does sometimes boost the pressure upward to slightly over 60psi or low 60's before the cranking actually starts.

Once again with the same senario as "MKO1976", manually priming via the air intake, will get the vehicle to start, pretty much withou fail, at least it has up until this point in time. Once started there is aboslutely no indication of fuel starvation what-so-ever and the pump (at an idle) keeps the pressure in the low 60's range. Lightly reving the engine, causes the pressure to jump higher into the mid to upper 60's momentarily while performing the reving. I have not yet performed a fuel pressure reading while driving on the road or with the return line pinched off.

Recently I've read and heard that there is a fuel pulsator, that may cause this problem, particularily if cracked (apparently inside the fuel tank, above the pump). Apparently the original equipment pulsator, can crack from fuel with too high of an ethanol mixture, and newer replacements are built to handle the higher levels. The maximum mixture I believe sold at normal gas pumps (not E-85) is a 15% mixture, which I'm sure I have had enough of, but I haven't ever put higher mix levels in, unless the wrong gas was in the regular fuel tanks at any given station. I suppose that is quite possible, but maybe unlikely...

The vehicle runs so very good (normal) once started, that I have no problems at all driving full highway speeds, even when towing my double axle 16' enclosed trailer down the road. Other than potential bleed back issues (like a weak or leaking check-valve or pulsator) it makes me wonder how the pump could perform so good once running, yet not perform up to par only at start-ups. I'm baffled with this one! Any further help or suggestions would be greatly appreciated! I was hoping someone has had the exact same problem as it seems that "MKO1976" and I have experienced and tell us what was done to resolve the issue, hopefully short of the entire fuel pump module replacement. I've also read that pump module replacement without the fuel pulsator replacement can lead to a repeat scenario? Actually I though a pump "Module" would incorporate the pulsator, though in reality it may not.

dmueller

I do not think they use a pulsator on yours.
But give us a make model year and engine on it.
Run the fuel pressure as I out lined in the upper post and post back readings.
MT

[wafrederick]

Needs a fuel pump and the fuel pressure spec is 60 psi.It will not run under 60 psi.Stay away from fuel pumps from AutoZone and Advanced.Cheap fuel pumps are not the way to go.Replacing the fuel filter when changing the fuel pump is part of the warrenty.

[Jeremy-WI]

dmueller's profile lists a 96 k1500, which should have a pulsator(actual part name is fuel pulse dampener). There should actually be a lot of info here with this same problem, doing a search in the suburban or tahoe forums may have something

[broughy84]

The first thing I would do would be check to make sure the regulator is good and then look for a leaking injector with a leak down test. If you turn the key several times on, off, on, off, on, off, on..... does the pressure eventually build to where it will start?