Hello again folks, hope your all keeping well and thank you to all who have replied to my previous posts.

Todays concern regards a strange pulsing of fuel whilst cruise at about 50 mph. I noticed it yesterday going up a slight incline.
I have read a few brief comments regarding a Fuel Pressure Regulator ( F.P.R. ) as a possible cause but what I didn't mention is that I can hear what sounds like a fuel pump straining behind me when the fuel pulsation comes into effect. There is also a slight delay in acceleration from a dead stop if I accelerate hard. I have instant accelaration, then a blip of nothing and then all good again.
Kind of a chicken or the egg issue for me as I'm cleuless. Would a faulty F.P.R. cause the fuel pump to strain and cause a whine or vise versa, would the fuel pump cause the F.P.R. to pulsate?
Thanks in advance
S. Degenkolb

 

It could be a blocked fuel filter, also, but I suspect the pump is failing. If you haven't changed the filter I would start there as it's the least expensive fix.

 

Thanks but I noticed when I bought the car 18 months ago it had a new fuel filter on it.

 

the fuel filter can certainly get plugged up very quickly if there is enough fine sediment in the fuel tank. Replacing it is inexpensive and an easy enough task. Always the logical first step to take when eliminating possible issues in the fuel system even though it had appeared to be newish.


Z

 

I'd say try and get some "numbers". Get a cheap ELM327 and a mobile app to check on the long term trims, both near idle and then with some rpm (say, 2k). High trims point to air leaks that can cause these hesitations. When air leaks are handled (do a smoke test to find them all), then consider a replacement air flow meter if the problem persists.

Also, try and record what happens to the short term trims during these events. If they shoot up, there is likely a temporary air leak. The noise you hear could be the pump trying to keep up with the extra air. The typical culprit here is the intake duct, as a small crack at idle can open wider under acceleration.

FWIW, I am working on another project car involving old gas and the situation is nasty. Tank and pump/float rusted, gas "separated" and left a layer of sticky tree sap-like glue everywhere. IOW, no amount of filter change and injector cleaner can remedy a severely aged tank and pump, sometime you have to just open stuff up and find out for yourself what it looks like in there.

Best of luck, keep us posted.

 

Ok here's the latest follow up. The car is no longer making an intermitant fuel pusling when cruising at 50 mph but I can still hear the fuel pump labouring to feed the engine when I just give it the slightest bit of throttle to maintain my speed of 50mph. The fuel pump is fine at all other times except maintaining cruising speeds at 50ish mph.
I did some minor changes noted below and also noticed that I no longer have a strong smell of fuel when I put my foot down to the floor which was always there previously.
Checked Dtc's, no codes to show.
Checked the Fuel Pressure Regulator vacuum hose for smell of fuel and there was none meaning the valve inside the unit is good.
Changed the thottle body gasket - possible damage to one I installed a few weeks ago for an unrelated issue.
Changed the Fuel Pump Relay

So me thinks the fuel pump is on it's way out but still working. Anyone replaced their's or know of a good aftermarket fuel pump?
Cheers

 

Question? Did you get a check engine light? When my fuel rail pressure sensor went bad I had the same pulsing at steady speeds (50-60) along with a check engine light. Changed the sensor on the rail in 5 minutes never had another issue.Think the sensor was around $50 from Rockauto.

 

Hi ShoreGuy. I didn't get a check engine light. In fact after a bit of tinkering the pulsing has now stopped but the droning noise is still coming from the fuel pump at cruising speed. Only when I try to maintain a constant speed though, otherwise I can't hear the fuel pump at all. So to sum up, I think the fuel pump is on it's way out.
Thanks for your input.

 

So just the noise now? If the car is running the way it should at cruising speeds could it be noise from something else? Wheel bearing, etc...Just seems strange that it is apparent more from speed instead of rpm.

 

Yes I know it is wierd but it's not just at 50mph as it happens any time I use the accelerator to maintain a cruising speed. I can hear the fuel pump behind me start to make a droning noise like it is struggling to feed the fuel at a constant presure.

 

Could it be a degraded or leaky hose internally in the tank? I’ve heard pumps labor when the hose between the pump body and the output flange leaks causing a pressure loss.

 

Has the car been sitting ? It seems every spring the fuel pump virus pops up when owners bring their cars out of hibernation. The fuel pressure regulator is a relatively minor fix compared to the job of replacing the fuel pump - just sayin'.

 

Yeah, I would have to agree from your description it does sound like the fuel pump. I have had a few go bad on me in the past. Good luck and let us know what you find.

Cheers!