Hard to start when cold?

The key is what is the fuel pressure when you try to start it cold? By "hard to start", if you mean it has a long crank time the first start of the day, it is likely fuel pressure is bleeding down. The fuel pump should run for roughly one second when you turn on the ignition switch. That's not enough time to get fuel pressure up for starting if it had bled down to 0 psi. You can get a clue by turning the ignition switch off instead of cranking the engine, turn it on a second time, THEN crank the engine. That gives the pump twice as much time to build pressure. The fuel pump will resume running as soon as you start cranking the engine, but since battery voltage is drawn down by the starter, the pump is going to run rather slowly. What little pressure might build up is too low to make the engine run, and it is bled off by the injectors almost as fast as it builds up.

When the engine is stopped, fuel pressure is supposed to hold for weeks. When it bleeds down over days or hours, there's three places to look. One is a leaking check valve in the pump assembly. You can verify that by using a hose pinch-off pliers to block the fuel supply hose where it's rubber transitioning from the body to the fuel rail on the engine. The second, less common cause is a leaking fuel pressure regulator. When that regulator is on the fuel rail, use the pinch-off pliers to block the fuel return line. That will be the smaller of the two hoses. When you pinch the hose going to the leaking item, the pressure will hold like it is supposed to.

The most common cause of loss of fuel pressure is a leaking injector. The best way to find that is to remove them while still attached to the fuel rail, then cycle the ignition switch to build pressure. Watch for the injector that becomes wet at the nozzle.

In rare instances any other leak in the fuel supply system will also cause fuel pressure to bleed down, but those causes are usually accompanied by a fuel smell. Look for wet hose connections, and smell around the injectors for signs of a leaking O-ring

Let me know what you find.

I'll check these items out and reply when I have it done. Thanks

Hi,

I noticed it has been a couple of days since we heard from you. Have you been able to make any progress? We are interested in knowing.

Thanks,

Joe

Sorry Joe, but with work and "other" projects to finish I haven't had the chance to get back to this. I hope to get into it again this coming weekend.

Hi,

No problem whatsoever. I'm just interested in knowing if you have been able to resolve the issue. When you get a chance, let me know.

Take care,

Joe

Well, it's been a couple weeks (almost) but put a fuel pressure gauge on it this afternoon, zero pressure at first after having sit for a week or so. 1st turn of the key pushes needle to 20psi. second turn of key gets it up to 40psi. still hard to start at first, running it goes back and forth between 30 - 40 PSI if I give it some pedal and sounds like it skipping a bit. I did see it drop from 20 - 0 psi after I turned switch off once, but only once. I'm leaning towards fuel pressure regulator bad. I did put a brand-new fuel pump assembly and new fuel filter in it last weekend (i work in auto parts, so I know new doesn't always mean good part). Ideas? Spec is 30-45 KOEO (Key on engine off). Is the specs I copy from another answer to a similar question on the site.

The pressures you listed are correct. It will drop down closer to 30 psi during coasting and will go up when the engine is under load and intake vacuum is low.

What was taking place when it was at 20 psi, and how long did it take to drop to 0 psi? Regardless what you have when you stop the engine, that pressure should hold for weeks, or at least days. To tell if the regulator is leaking, follow the smaller fuel hose from the rail to where it turns into a rubber hose, and pinch that off. Fuel pressure will go to max with the engine still running. Now stop the engine and see if pressure drops off. If it does, the best suspect is a leaking injector. With a leaking injector, pressure typically does not drop to 0 psi instantly. It can take as much as a minute or even longer. If pressure does drop instantly when the engine is stopped, the check valve in the pump assembly is the better suspect.

Thanks for the reply. I decided sense gas tank is original and i had to clean out a lot of rust I'm getting a brand-new tank and new fuel filter the cost on both are not bad really (still in budget for this project) and a new fuel pressure regulator and a set of new injectors. I'm pretty sure the skip is from the vacuum leak I haven't located yet.

Dandy. When you replace the fuel pump, there's two ways to do it. One is to replace the entire housing with the pump in it. If you do it that way, you're all set. The other way is to buy just the pump and motor and transplant that into the original housing. That is okay too, but there's two things to be aware of. The first is the pick-up screen on the bottom of the housing. Those are very inexpensive but they can cause a really elusive problem of stalling when the largest volume of fuel is being pumped, which is during coasting. Be sure to replace that piece. It's commonly referred to as a "strainer".

The second thing is to look for a rubber hose inside the housing. I don't remember the models affected, but Ford had some problems with that hose dry-rotting and letting air get sucked in. There was a magic fuel level at which it caused engine performance problems. If the tank had a higher fuel level, gas got sucked in instead of air, so no performance problem showed up at that time. If you see a rubber hose and it looks deteriorated, replace that too.

Sorry for the confusion here, I am 98stangcoupev6. My login somehow got all messed up and I didn't wright it down, so I created this new one. Got a few more parts coming in. Updates coming soon.

I do have between 35-39 PSI on fuel pressure. Got a few more parts in and yesterday I installed a new fuel tank (old one had so much rust in it). It took forever to get it started so I could move it and install the new tank. I had to use starting fluid and it finally started. After I moved it to where I was to work on it, turned it off and it fired right back up (head scratcher). I have a new fuel regulator and set of injectors; I'll install them soon. It almost sounds like either the cam or crank sensor isn't working but I do not have any codes.

Hi,

If it is a cam sensor, it will set a code. On the other hand, a crankshaft position sensor may or may not by design. However, if it is the crankshaft position sensor, you will lose the ignition spark to the spark plugs. Thus, it won't start even with starting fluid.

When it doesn't start until starting fluid is used, to me that indicates a fuel-related issue.

Let me know how things turn out for you or if there is anything I can do to help.

Take care,

Joe

I hope to get the fuel pressure regulator and injectors replaced in the next day or two. I did use a vacuum smoker and didn't see any leaks.

Hi,

Thanks for the update. Were you able to confirm the issue with fuel pressure? I'm interested in knowing.

Take care,

joe

Well, I can't seem to remember to write my login info down (i did this time). I'm 98stangcoupev6 and 1998stangcoupev6. Long story short. After replacing the fuel tank (it had more rust in it than fuel) fuel pump and filter and 5 gals of clean fuel I went outside yesterday morning to install the new injectors and spark plugs. It was around 40 degrees and I thought what the heck I'll try it to see just for kicks. Turn the key and let the fuel pump do its thing, and it fired right up with no issues, and it's been sitting for over 4 days sense I replaced tank and pump etc. 39 PSI is pressure reading. I don't know if all the rust was blocking the pump pickup, or it just didn't have enough fuel. Going to see if it will start again this morning so I can drive it to work. Let ya'll know later today.

Hi,

Thanks for the update. Yes, I feel that was likely the cause. Keep in mind that the pump draws at a higher pressure so if there is dirt/rust, it's going to try to move it as well.

Let me know how it ran today. Also, if you haven't replaced the fuel filter, that should be done as well.

Take care,

Joe

It started up great yesterday morning and I drove it to work. A new tank, pump and filter have been installed. Scratch this issue off the list now on to A/C selector and front suspension.

Hi,

Thanks for the update. I'm glad to know it's running properly again.

Take care of yourself. I will watch for the new posts for the suspension and A/C issues.

Joe